Updated old user management routes to only be accessible with permission
to manage users, so also removed old content controls checking for that
permission.
Ensures some sensible text is always in webhook text data.
Also aligned some notification reporting to use centralised activity
system instead of custom success events.
For #4216
This is to encourge the ":count" values to be used instead of 1s in the
translated variants so that non-pluralised languages are hardcoded with
"1"s in their content, even when not used in a singular context.
For #4040
Altered & updated permissions repo, and existing connected
RoleController to suit.
Also extracts in-app success notifications to auto activity system.
Tweaked tests where required.
