We use a custom backend because the user must be able to supply a email
or username to the login form. We will find out ourself what they
supplied.
Returns the user User.
Arguments
- identification
- A string containing the username or e-mail of the user that is trying
to authenticate.
Keyword arguments
- password
- Optional string containing the password for the user.
- check_password
- Boolean that defines if the password should be checked for this user.
Always keep this True. This is used at activation when a user opens
a page with a secret hash.