Document gitlab architecture / installation / operation

Now gitlab is deployed and used in production, we should add some documentation on how to operated it

added Documentation environment: production labels

assigned to @vsellier

marked this issue as related to #4063 (closed)

changed title from Document gitlab architecture / installation / operatio to Document gitlab architecture / installation / operation

added state:wip label

Diff D8809 created

Documentation landed

closed

removed state:wip label