Refactor add/remove service calls

[anncatton]

Some of these services calls are not using the correct api route when adding/removing child entities from their parents. This is resulting in multiple api calls being made.
For example: removing 2 users from a group will make two requests, one for each user, using the users/{id}/groups/{id} DELETE endpoint instead of one call to the groups/{id}/users/{ids} DELETE endpoint.

The Ego api allows for multiple ids to be sent in these types of requests. Some investigation may be required as to why this was implemented this way on the ui side. If it was due to how the code was originally structured, hopefully this can remedied in the refactoring done in #199, #200, and #201. This issue should likely be fixed as an enhancement once this other work is completed.