Login name with space or maybe other unusual characters causes problems

Currently it is possible to create a user in translate5 with a space in the login name.

But when entering this login name to reset a password, translate5 does not accept the name.

Please make sure, that newly created login names via GUI or API in the future only can contain word characters (regex for a word). In this case we need a migration script to change existing login names, that may not longer be supported. The script should also mail the users their new login name.

Alternatively in the future support all login name possibiliies everywhere, where they need to be entered. And ensure, that allowed characters can not cause any trouble.

Please decide together, what solution makes more sense.

Please develop this together with Aleks as a peer, who just was working on the related forms for the password.