This is exploration for read-only mode, which is a feature to allow admins to disable functionality which would disrupt RB upgrades and maintenance while allowing users to consume site content.
Blocking API and introducing feature into admin panel are in previous commits.
Changes to Navbar (New Review Request link), Actions in ReviewRequestEditorView, ReviewRequestEditorView description, testing, information, comments, diff/comment box all changed.
Sidebar in Dashboard disabled (possibly not the best way to disable those features).
ETag updated to reflect changes in read-only mode for ReviewRequestEditorView.