feat(metamodel): generate indexed subfields for @Reference fields (#677)

[bsbodden]

When a document has a @reference @indexed field pointing to another entity, the metamodel now generates field accessors for the referenced entity's @indexed and @searchable fields. This enables queries like:

entityStream.of(RefVehicle.class)
.filter(RefVehicle$.OWNER_NAME.eq("John"))

Changes:

• MetamodelGenerator: Add processReferencedEntityIndexableFields() to traverse referenced entities and generate subfield accessors
• RediSearchIndexer: Add createIndexedFieldsForReferencedEntity() to create search index fields for referenced entity properties

For example, given:
@document class Owner { @searchable String name; @indexed String email; }

@document class RefVehicle { @reference @indexed Owner owner; }

The RefVehicle$ metamodel now includes:

• OWNER_NAME (TextField)
• OWNER_EMAIL (TextTagField)

Note: @reference fields store only the entity ID, not the full embedded object. To actually search by referenced entity properties, the data must be denormalized or the query should use ReferenceField.eq(entity).

Closes #677

[Copilot]

Pull request overview

This PR adds support for generating indexed subfields for @Reference fields in the metamodel, enabling queries on referenced entity properties. When a document has a @Reference @Indexed field pointing to another entity, the metamodel now generates field accessors for the referenced entity's @Indexed and @Searchable fields.

Key Changes

• MetamodelGenerator: Added processReferencedEntityIndexableFields() to traverse referenced entities and generate subfield accessors for indexed/searchable fields
• RediSearchIndexer: Added createIndexedFieldsForReferencedEntity() to create search index fields for referenced entity properties
• Test fixtures: Added Owner, RefVehicle models and repositories, along with comprehensive tests to verify metamodel generation and query behavior

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
redis-om-spring/src/main/java/com/redis/om/spring/metamodel/MetamodelGenerator.java	Added processReferencedEntityIndexableFields() method to generate metamodel fields for referenced entity's indexed fields
redis-om-spring/src/main/java/com/redis/om/spring/indexing/RediSearchIndexer.java	Added createIndexedFieldsForReferencedEntity() method to create index fields for referenced entity properties
tests/src/test/java/com/redis/om/spring/fixtures/document/model/Owner.java	New test fixture representing an entity with indexed fields that can be referenced
tests/src/test/java/com/redis/om/spring/fixtures/document/model/RefVehicle.java	New test fixture with a @Reference @Indexed field to Owner, demonstrating the feature
tests/src/test/java/com/redis/om/spring/fixtures/document/repository/OwnerRepository.java	Repository for Owner entity
tests/src/test/java/com/redis/om/spring/fixtures/document/repository/RefVehicleRepository.java	Repository for RefVehicle entity
tests/src/test/java/com/redis/om/spring/annotations/document/ReferenceIndexedSubfieldsTest.java	Comprehensive tests verifying metamodel field generation and query behavior for referenced entity fields

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

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