feat: Update contract tests to support multiple synchronizers and initializers (#222)

**Requirements**

- [ ] I have added test coverage for new or changed functionality
- [ ] I have followed the repository's [pull request submission
guidelines](../blob/main/CONTRIBUTING.md#submitting-pull-requests)
- [ ] I have validated my changes against all supported platform
versions

**Related issues**

Related to sdk-test-harness commit:
launchdarkly/sdk-test-harness@01a245c

**Describe the solution you've provided**

Updates the contract test implementation to match the sdk-test-harness
changes that add support for multiple synchronizers (more than 2) for
testing fallback scenarios.

Contract test model changes:
- Changed `SdkConfigDataSystemParams.Synchronizers` from
`SdkConfigSynchronizersParams` (with `Primary`/`Secondary` properties)
to `SdkConfigDataSynchronizerParams[]` (array)
- Removed the `SdkConfigSynchronizersParams` class
- Renamed `SdkConfigSynchronizerParams` to
`SdkConfigDataSynchronizerParams` for consistency
- Updated `SdkClientEntity.BuildSdkConfig` to iterate over the
synchronizers array

CI config change:
- Pinned FDv2 contract tests to use the `v3.0.0-alpha.3` tag of
sdk-test-harness instead of the `feat/fdv2` branch

**Human review checklist**

- [ ] Verify `v3.0.0-alpha.3` tag exists in sdk-test-harness and is
compatible with the array-based synchronizer format used here
- [ ] Verify the FDv1 fallback synchronizer selection logic is correct —
it now picks the first polling synchronizer found in the array, or falls
back to the first synchronizer if none have polling configured
- [ ] Confirm the JSON serialization matches what the test harness sends
(property names are auto-camelCased)

**Describe alternatives you've considered**

Could have kept backward compatibility by supporting both the old
Primary/Secondary structure and the new array format, but this would add
unnecessary complexity since the test harness has moved to the
array-based approach.

**Additional context**

- Link to Devin run:
https://app.devin.ai/sessions/5d71cc37cb45475088773207ef7fd987
- Requested by: rlamb@launchdarkly.com

This is a contract test and CI config change only — no changes to the
SDK itself.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Moderate risk due to a breaking change in the contract-test config
model (`Synchronizers` shape) and updated fallback-selection behavior
that could alter FDv2/FDv1 test execution, though it is confined to
test/CI code.
> 
> **Overview**
> Updates the contract test data-system configuration model to support
**multiple** synchronizers by changing
`SdkConfigDataSystemParams.Synchronizers` from a `Primary`/`Secondary`
object to an array of `SdkConfigDataSynchronizerParams` (and
removing/renaming the old types).
> 
> Adjusts `SdkClientEntity.BuildSdkConfig` to build all provided
synchronizers, and changes FDv1 fallback selection to pick the *first
polling* synchronizer found (otherwise the first synchronizer). CI’s
FDv2 contract test action is also updated to run `sdk-test-harness` from
the pinned `v3.0.0-alpha.3` tag instead of the `feat/fdv2` branch.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
349d410. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: rlamb@launchdarkly.com <rlamb@launchdarkly.com>

Author: devin-ai-integration[bot]

.github/actions/contract-tests/action.yml

@@ -12,7 +12,7 @@ inputs:
     required: false
     default: ''
   run_fdv2_tests:
-    description: 'Whether to run contract tests from the feat/fdv2 branch'
+    description: 'Whether to run contract tests from the v3.0.0-alpha.3 tag'
     required: false
     default: 'false'
 
@@ -64,15 +64,15 @@ runs:
       shell: bash
       run: dotnet ${{ inputs.service_dll_file }} > test-service.log 2>&1 & disown
 
-    - name: Clone and run contract tests from feat/fdv2 branch
+    - name: Clone and run contract tests from v3.0.0-alpha.3 tag
       if: inputs.run_fdv2_tests == 'true'
       shell: bash
       run: |
         mkdir -p /tmp/sdk-test-harness
         git clone https://github.com/launchdarkly/sdk-test-harness.git /tmp/sdk-test-harness
         cp $(dirname ./${{ inputs.service_project_file }})/test-supressions-fdv2.txt /tmp/sdk-test-harness/testharness-suppressions-fdv2.txt
         cd /tmp/sdk-test-harness
-        git checkout feat/fdv2
+        git checkout v3.0.0-alpha.3
         go build -o test-harness .
         ./test-harness -url http://localhost:8000 -debug -status-timeout=360 --skip-from=testharness-suppressions-fdv2.txt --stop-service-at-end
       env:

pkgs/sdk/server/contract-tests/Representations.cs

@@ -152,7 +152,7 @@ public class SdkConfigDataSystemParams
         public SdkConfigDataStoreParams Store { get; set; }
         public int? StoreMode { get; set; }
         public SdkConfigDataInitializerParams[] Initializers { get; set; }
-        public SdkConfigSynchronizersParams Synchronizers { get; set; }
+        public SdkConfigDataSynchronizerParams[] Synchronizers { get; set; }
         public string PayloadFilter { get; set; }
     }
 
@@ -185,13 +185,7 @@ public class SdkConfigDataInitializerParams
         public SdkConfigPollingParams Polling { get; set; }
     }
 
-    public class SdkConfigSynchronizersParams
-    {
-        public SdkConfigSynchronizerParams Primary { get; set; }
-        public SdkConfigSynchronizerParams Secondary { get; set; }
-    }
-
-    public class SdkConfigSynchronizerParams
+    public class SdkConfigDataSynchronizerParams
     {
         public SdkConfigStreamingParams Streaming { get; set; }
         public SdkConfigPollingParams Polling { get; set; }

pkgs/sdk/server/contract-tests/SdkClientEntity.cs

@@ -487,27 +487,16 @@ private static Configuration BuildSdkConfig(SdkConfigParams sdkParams, ILogAdapt
                 }
 
                 // Configure synchronizers
-                if (sdkParams.DataSystem.Synchronizers != null)
+                if (sdkParams.DataSystem.Synchronizers != null && sdkParams.DataSystem.Synchronizers.Length > 0)
                 {
                     var synchronizers = new List<IComponentConfigurer<IDataSource>>();
 
-                    // Primary synchronizer
-                    if (sdkParams.DataSystem.Synchronizers.Primary != null)
+                    foreach (var synchronizerParams in sdkParams.DataSystem.Synchronizers)
                     {
-                        var primary = CreateSynchronizer(sdkParams.DataSystem.Synchronizers.Primary, sdkParams.DataSystem.PayloadFilter);
-                        if (primary != null)
+                        var synchronizer = CreateSynchronizer(synchronizerParams, sdkParams.DataSystem.PayloadFilter);
+                        if (synchronizer != null)
                         {
-                            synchronizers.Add(primary);
-                        }
-                    }
-
-                    // Secondary synchronizer (optional)
-                    if (sdkParams.DataSystem.Synchronizers.Secondary != null)
-                    {
-                        var secondary = CreateSynchronizer(sdkParams.DataSystem.Synchronizers.Secondary, sdkParams.DataSystem.PayloadFilter);
-                        if (secondary != null)
-                        {
-                            synchronizers.Add(secondary);
+                            synchronizers.Add(synchronizer);
                         }
                     }
 
@@ -517,23 +506,22 @@ private static Configuration BuildSdkConfig(SdkConfigParams sdkParams, ILogAdapt
 
                         // Find the best synchronizer to use for FDv1 fallback configuration
                         // Prefer polling synchronizers since FDv1 fallback is polling-based
-                        SdkConfigSynchronizerParams synchronizerForFallback = null;
+                        SdkConfigDataSynchronizerParams synchronizerForFallback = null;
 
-                        // First, try to find a polling synchronizer (check secondary first, then primary)
-                        if (sdkParams.DataSystem.Synchronizers.Secondary != null && 
-                            sdkParams.DataSystem.Synchronizers.Secondary.Polling != null)
+                        // First, try to find a polling synchronizer
+                        foreach (var syncParams in sdkParams.DataSystem.Synchronizers)
                         {
-                            synchronizerForFallback = sdkParams.DataSystem.Synchronizers.Secondary;
-                        }
-                        else if (sdkParams.DataSystem.Synchronizers.Primary != null && 
-                                 sdkParams.DataSystem.Synchronizers.Primary.Polling != null)
-                        {
-                            synchronizerForFallback = sdkParams.DataSystem.Synchronizers.Primary;
+                            if (syncParams.Polling != null)
+                            {
+                                synchronizerForFallback = syncParams;
+                                break;
+                            }
                         }
-                        // If no polling synchronizer found, use primary synchronizer (could be streaming)
-                        else if (sdkParams.DataSystem.Synchronizers.Primary != null)
+                        
+                        // If no polling synchronizer found, use the first synchronizer (could be streaming)
+                        if (synchronizerForFallback == null && sdkParams.DataSystem.Synchronizers.Length > 0)
                         {
-                            synchronizerForFallback = sdkParams.DataSystem.Synchronizers.Primary;
+                            synchronizerForFallback = sdkParams.DataSystem.Synchronizers[0];
                         }
 
                         if (synchronizerForFallback != null)
@@ -563,7 +551,7 @@ private static Configuration BuildSdkConfig(SdkConfigParams sdkParams, ILogAdapt
         }
 
         private static IComponentConfigurer<IDataSource> CreateSynchronizer(
-            SdkConfigSynchronizerParams synchronizer,
+            SdkConfigDataSynchronizerParams synchronizer,
             string payloadFilter)
         {
             if (synchronizer.Polling != null)
@@ -608,7 +596,7 @@ private static IComponentConfigurer<IDataSource> CreateSynchronizer(
         }
 
         private static IComponentConfigurer<IDataSource> CreateFDv1FallbackSynchronizer(
-            SdkConfigSynchronizerParams synchronizer)
+            SdkConfigDataSynchronizerParams synchronizer)
         {
             // FDv1 fallback synchronizer is always polling-based
             var fdv1PollingBuilder = DataSystemComponents.FDv1Polling();