Added new Associations.isUriResolvableAssociation() method that separates URI resolvability from HTTP endpoint exposure.

[ruthst00]

Fixes #1515

Root Cause: When the ANNOTATED repository detection strategy is active, repositories without @RepositoryRestResource have isExported() == false. The AssociationUriResolvingDeserializerModifier in both PersistentEntityJacksonModule and PersistentEntityJackson2Module used Associations.isLinkableAssociation() to decide whether to register a UriStringDeserializer for association properties. That method checks metadata.isExported() for the target type — which returns false under ANNOTATED for un-annotated repositories. The deeper issue was that PersistentPropertyResourceMapping.isExported() also checks the target type's export status, creating a chain where ownerMetadata.isExported(property) returned false even for the owner's property check. As a result, UriStringDeserializer was never registered and Jackson threw a JsonMappingException (400 Bad Request) when a URI string was submitted for the association.

Fix: A new Associations.isUriResolvableAssociation() method separates URI resolvability from HTTP endpoint exposure. It returns true whenever a ResourceMetadata (i.e. a repository) exists for the target type, regardless of export status. The owner-level check only looks for an explicit @RestResource(exported = false) annotation on the property itself — bypassing the circular dependency where the target type's export status would prevent URI deserialization. Both Jackson modules now use isUriResolvableAssociation() for deserialization while isLinkableAssociation() continues to be used for serialization (link rendering), where the HTTP export check is correct and intentional.

Test coverage added (9 files, 586 lines):

• AssociationsUnitTests: 4 new unit tests for isUriResolvableAssociation (all 14 tests pass)
• AnnotatedStrategyUriDeserializationIntegrationTests: Full JPA integration test with Member/@ManyToOne Profile scenario — all 3 tests pass: POST succeeds (201), /profiles returns 404 (not exposed), /members returns 200 (exposed)

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