Provide an alter for user settings

Added a simple patch for now.
I guess it should be updated to use DI.

It would be a good option to alter user data before saving

can you provide a real life scenario of this being useful?

Everything in the user data that I can think of (TFA metadata, seeds) is essentially self owned/internal (to a plug-in) data that shouldn’t be touched by external actors.

basically, I need an option/event to check when the tfa status (1/0) has been changed.

I suspect ✨ User account should be marked as updated when TFA is updated Active may end up being a dedicated TFA event (as I’m not aware of a specific user save event we could leverage) however nothing about that has been formally said in that issue.

If you want to rescope this issue: I can see TFA emitting an Event when we enable/disable TFA for a user or a specific plugins is provisioned for a user as making a significant amount of sense without using the hook system (especially not using alter hooks).