Removed JPA and used Postgresql ltree extension

gms/pom.xml

gms/src/main/java/it/inaf/ia2/gms/authn/SessionData.java

...ain/java/it/inaf/ia2/gms/controller/GroupsController.java

...ava/it/inaf/ia2/gms/controller/PermissionsController.java

gms/src/main/java/it/inaf/ia2/gms/model/GroupNode.java

.../main/java/it/inaf/ia2/gms/model/GroupsModelResponse.java

gms/src/main/java/it/inaf/ia2/gms/model/Permission.java

gms/src/main/java/it/inaf/ia2/gms/persistence/GroupsDAO.java

...in/java/it/inaf/ia2/gms/persistence/GroupsRepository.java

...ava/it/inaf/ia2/gms/persistence/MembershipRepository.java

...main/java/it/inaf/ia2/gms/persistence/MembershipsDAO.java

...main/java/it/inaf/ia2/gms/persistence/PermissionsDAO.java

...va/it/inaf/ia2/gms/persistence/PermissionsRepository.java

...ain/java/it/inaf/ia2/gms/persistence/UsersRepository.java

...n/java/it/inaf/ia2/gms/persistence/model/GroupEntity.java

...in/java/it/inaf/ia2/gms/persistence/model/Membership.java

...a/it/inaf/ia2/gms/persistence/model/MembershipEntity.java

.../java/it/inaf/ia2/gms/persistence/model/MembershipId.java

...a/it/inaf/ia2/gms/persistence/model/PermissionEntity.java

...src/main/java/it/inaf/ia2/gms/persistence/model/User.java