Add the capability to add or remove group members through API

[pchevali]

Is your feature request related to a problem? Please describe.
To automate the creation of groups there is a CRUD api, however, it is not possible to change the group members through a rest api. There is only a GET function implemented for members. It seems to be by design.

Describe the solution you'd like
Being able to manage the group members through api. Add a user to the group and remove the user from a group

Describe alternatives you've considered
There is form handler route pointing to group/{slug}/member_add