Add optional username and email synchronization from identity provider

It turns out that this was skipped on the codebase.
These changes remove that skipping.

After that, and changing configuring to add mappings, I verified that both username and its e-mail are changed on login.

New commits on new 3452530-name-email-sync topic branch and related new MR !111.

- 130217f Allow mapping user name and email from IdP

This works as advertised.