Also, mutualize AccessRequests and Members endpoints for Group &
Project.
New API documentation for the AccessRequests endpoints.
Signed-off-by: Rémy Coutable <remy@rymai.me>
This is to ensure we don't send unwanted notifications when deleting a
project. In other words, stop abusing AR callbacks and use services.
Signed-off-by: Rémy Coutable <remy@rymai.me>