Completes testing for SGF-260, which enables the Spring Data Commons @Id...

... mapping annotation to be used on methods of domain interfaces or classes in addition to domain entity class fields.  These test additions require DATACMNS-476 (https://jira.spring.io/browse/DATACMNS-476), with details in GitHub PR #76 (https://github.com/spring-projects/spring-data-commons/pull/76) to be included in the recent SDC 1.8.0.BUILD-SNAPSHOT, slated for the Spring Data Dijkstra release as M1.