and migrate affected code _last refactoring bits to replace **util.OptionalBool** with **optional.Option[bool]**_ (cherry picked from commit a3f05d0d98408bb47333b19f505b21afcefa9e7c) Conflicts: services/repository/branch.go trivial context conflict
Currently we can add webhooks for organizations but not for users. This PR adds the latter. You can access it from the current users settings. 
This add system hook API