fixes #5780 - API v2 - RESTful way to add/remove many-to-many association one at a time rather than passing all id's

Note: Related to PR https://github.com/theforeman/foreman/pull/1773 to add auditing when adding/removing
IMHO in REST the multiple value actions should be performed on a collection resource:
"/environments/:environment_id/links/organizations?id=3&id=6&id=9"