fix(project): encode project_ip_access_list ID via EncodeStateID

[nilpntr]

Description of your changes

mongodbatlas_project_ip_access_list configured its GetIDFn (in config/resources/project.go) to build a plain "<project_id>-<entry>" terraform ID:

return fmt.Sprintf("%s-%s", project, ip), nil

But terraform-provider-mongodbatlas (v2.x, plugin-framework) reads this resource with conversion.DecodeStateID and rejects any ID that doesn't decode to exactly {project_id, entry}:

decodedIDMap := conversion.DecodeStateID(...)
if len(decodedIDMap) != 2 {
    resp.Diagnostics.AddError("error during the reading operation", "the provided resource ID is not correct")
}

So every observe fails:

observe failed: cannot run refresh: refresh failed: error during the reading
operation: the provided resource ID is not correct

And because GetIDFn returns a non-empty ID from parameters, upjet runs the refresh on the first reconcile and never reaches Create — the access-list entry is never added and the MR is stuck Synced=False with an empty crossplane.io/external-name.

This is the same EncodeStateID scheme the repo already handles for other Atlas resources via encodedStateID. This PR:

• Adds config.projectIPAccessListExternalName(), which builds the ID with the existing encodeAtlasStateID helper (keys entry + project_id). The entry value comes from either cidr_block or ip_address (mutually exclusive), which the static encodedStateID/encodedStateIDMapped helpers can't express — hence a small dedicated config rather than a map entry.
• Points "mongodbatlas_project_ip_access_list" at it in externalNameConfigs (was config.IdentifierFromProvider).
• Removes the stale plain-format GetIDFn override in config/resources/project.go so the default external-name config applies (References/LateInitializer kept).
• Adds unit tests covering both cidr_block and ip_address, the two-key round-trip through DecodeStateID, the error paths, and entry recovery from external-name.

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable test to ensure this PR is ready for review.

Ran go build ./config/... and go test ./config/... locally (all pass). Full make reviewable left to CI.

How has this code been tested

• Unit tests in config/external_name_test.go (TestProjectIPAccessListGetIDFn, TestProjectIPAccessListGetIDFn_Errors) — assert the encoded ID decodes back to exactly {project_id, entry} for both cidr_block and ip_address.
• Verified live against a real MongoDB Atlas project with provider built from this branch (bundling terraform-provider-mongodbatlas v2.12.0): the IPAccessList MR reconciles to Synced=True/Ready=True and the entry appears in the project's access list. Before the fix the same MR failed with the provided resource ID is not correct.

[fernandezcuesta]

Hi @nilpntr, first of all thanks for your contribution!
If I'm not mistaken, this issue -among others- should be fixed in #128 which I plan to release soon in v1.2. Let me know if after the new version is cut you still experience any issues with this resource.

Thanks!

[fernandezcuesta]

Closing this one as it was included in #128