==== Motivation
It would be really confusing to have regular, permanent, registered accounts whose usernames mimic the style of https://www.mediawiki.org/wiki/Help:Temporary_accounts
We should prevent people from accidentally creating a matching username. This means preventing the creation of anything that begins with a `~YYYY-n` format.
Before testwiki deployment we will only migrate usernames beginning with "**~2**" (there are only two such accounts based on the analysis in T346465. After testwiki deployment we will consider migrating all other usernames so that the identifier can be simple "**~**".
See also {T332805}.
==== What needs doing
[] Get a list of all accounts starting with ~ {T346465}
[] Define the config for `matchPattern`, `reservedPattern` and `genPattern`
[] Rename any users necessary