CLEANUP: Remove API routes that are not used

[tiblu]

TODO

NOTE: Verify usage against application logs!

• REMOVE API: GET /api/users/:userId/groups/:groupId/topics, which is replaced by GET /api/users/:userId/groups/:groupId/members/topics
• REMOVE API ROUTE: GET/POST /api/users/:userId/groups/:groupId/members which is replaced by /api/users/:userId/groups/:groupId/members/users
• REMOVE API ROUTE: PUT/DELETE /api/users/:userId/groups/:groupId/members/:userId which is replaced by /api/users/:userId/groups/:groupId/members/users/:userId

[ilmartyrk]

Still relevant, this list should be updated and fixed

[anettlinno]

Triage 37. Check API code and harvest out those end points and parts of code that we don´t use any more. Approx. dev. time 1h. Sending to development.

[BeccaMelhuish]

@ilmartyrk will assume OK to go to 'later' as old, dormant issue