Entity Get Process

[EntityReadHandler.get_entity - read.py]
+--> Validate Clients: Check vitess_client and s3_client are initialized (503 if not)
+--> Validate Entity: Check entity_exists(entity_id) in Vitess (404 if not)
+--> Get Head Revision: head_revision_id = vitess_client.get_head(entity_id) (404 if 0)
+--> Read Revision: revision = s3_client.read_revision(entity_id, head_revision_id)
+--> Check Deleted: If state.is_deleted is True, return 404
+--> Build Response: EntityResponse with id, rev_id, data, and state flags
+--> Return: EntityResponse