Allow site-admin to remove themselves from an Org CLOUD-262
Created by: rafax
Allow site-admin to remove themselves even if they are the last member of an Org - CLOUD-262.
Tested:
- site admin can remove themselves (in UI and API)
- site admin cannot remove last user if they are not a member of an Org (through API)
- regular user cannot remove themselves if they are the last member (through API)