OOO status to auto-decline assignments

Background

• At GitLab, we are remote, so it's often hard to know if another team member is OOO on vacation and is not actively working.
• So it would be great to auto-decline assignments of work, such as being assigned to an issue or a merge request.

Proposal

• Have some type of option in your profile for OOO mode, similar to Google Calendar.
• In this first iteration, the status is either on or off, and there's time bound. You are just always in this mode or not. You have to explicitly turn it off.
• There should be some UI to tell people you are in this mode (in addition to the personal settings), such as maybe a special emoji or part of the tooltip when you hover over your username.
• When you attempt to assign an issue or merge request to this person, GitLab will tell you that this isn't possible.