Add new CacheableDSpaceObject abstract class for Hibernate second-level caching. Required in Hibernate 6 as subclasses cannot use @Cache annotation

dspace-api/src/main/java/org/dspace/content/Collection.java

@@ -52,7 +52,7 @@ import org.dspace.eperson.Group;
  */
 @Entity
 @Table(name = "collection")
-public class Collection extends DSpaceObject implements DSpaceObjectLegacySupport {
+public class Collection extends CacheableDSpaceObject implements DSpaceObjectLegacySupport {
 
     @Column(name = "collection_id", insertable = false, updatable = false)
     private Integer legacyId;