Option to enable self approval of merge requests at a project level

Description

We use 'group' branches for staging related work before it hits master. For example, a large feature might be 'feature/group' with specific tasks as 'feature/task-1' and 'feature/task-2'. All of the task branches are merged into the group branch via merge requests. To ensure that no integration issues have crept in, prior to the merge to 'master' we also issue a merge request for the group branch. At this point, the merge request contains commits from several developers. In our team, anyone can create the group merge request with the expectation that that person will also participate in its review.

However, the creator of the group merge request cannot indicate their approval of the merge via the standard mechanism, as this is restricted by Gitlab. This means that the true review and approval status of the merge request is not reflected or recorded accurately.

Proposal

Add an option at the project level to allow creators of merge requests to also approve them. As a small team, we can manage the sensibilities of who is a valid approver via separate mechanisms and do not need this enforced at the software level.

Links / references

Note that this is very similar to #966 (closed), but not limited to 'masters' and controlled via a project setting.

Design

• If Enable self-approval of merge requests is on, authors will simply be able self-approve, and they see the approve UI.
• The question icon links to the documentation (The documentation doesn't exist now).