* Copy the add_members method to the new join method
* Remove unneeded code from the join method
* Rearrange the join method
* Remove unneeded stuff from the add_members method
* Extract add_user_to_group method
* Implement of the client side
* Tests
* Doesn't inline users.uniq
* Return promise from join.then()
* Remove unnecessary begin and end
* Revert "Return promise from join.then()"
This reverts commit bda84d8d
* Remove variable already_in_group