Pass a URL in to set the destination a user should be redirected to upon
logging in.
If no parameter is passed, gets the authentication redirect URL. The URL
returned is as per following rules:
- Returns the normalized redirect URL from storage if it is
present and for the same domain the current app is running on.
- If there is no URL returned from storage and there is a config
loginRedirect, the loginRedirect value is returned.
- If there is no session and no loginRedirect, / is returned.