Add an indicator when Admin Mode is enabled

Release notes

Add a visual indicator to the user when Admin mode is currently activated.

Problem to solve

In the context of a user that has Admin privileges on a GitLab instance and the Admin Mode feature is enabled.

When the user "Turn on Admin Mode" for his current session, there is no visible indicator that he is in this mode. This can lead to unwanted action when not careful.

Proposal

Add a visual indicator of the current state of the Admin mode for the current user.

Here are two visual proposals :

Intended users

Sidney (Systems Administrator)

Feature Usage Metrics

Nothing more than the actual Admin Mode feature