Allow changing the backend of the importing user to DB

[IljaN]

Assuming you have an installation with LDAP or SAML, you might want to import just one LDAP user to a new installation.
Currently you need to use the same LDAP app in both servers (the specific version might be different) with the same configuration (specifically the userid), so the same user is found in both servers. If somehow the user isn't found, the import will fail.

We can add an explicit option to try to create a DB user with the same information as the LDAP user. Combining with the alias option, we can move user from any provider to the DB.

Note that there are no plans about how this should be implemented at the moment.