Disable URLConnection cache

This commit further implements the ability to disable JAR file caching
when loading Smithy models. This is necessary to make loading models
from JARs when using build tools like Gradle more reliable.

Author: mtdowling

smithy-model/src/main/java/software/amazon/smithy/model/loader/ModelAssembler.java

@@ -304,7 +304,11 @@ public ModelAssembler addImport(URL url) {
         Objects.requireNonNull(url, "The provided url to ModelAssembler#addImport was null");
         inputStreamModels.put(url.toExternalForm(), () -> {
             try {
-                return url.openStream();
+                URLConnection connection = url.openConnection();
+                if (properties.containsKey(ModelAssembler.DISABLE_JAR_CACHE)) {
+                    connection.setUseCaches(false);
+                }
+                return connection.getInputStream();
             } catch (IOException | UncheckedIOException e) {
                 throw new ModelImportException("Unable to open Smithy model import URL: " + url.toExternalForm(), e);
             }