Registration date not stored when using Mnesia

[Dunedan]

Environment

• ejabberd version: 23.01
• Erlang version: Erlang (SMP,ASYNC_THREADS) (BEAM) emulator version 13.1.5
• OS: Linux (Debian)
• Installed from: distro package

Bug description

When using an SQL database backend, the users table contains a created_at column, containing the timestamp of the user registration. That doesn't seem to be the case when using Mnesia as database backend, as there isn't such a field in the passwd table. Having the registration date available when using Mnesia as well would be quite valuable.

Also with the current behavior, when using the export2sql command to migrate from Mnesia to an SQL database, this results in created_at being populated with the date of the migration, instead of the registration date or no date at all, leading to wrong registration dates after the migration.