Pass the User instance to hook methods

[tchaumeny]

This is related to issue #163

With this new signature, we can implement hooks to check user may log in using SAML for instance:

def before_login_hook(user_identity, target_user):
    """Check user SAML flag"""
    if not target_user.saml_login_enabled:
        raise PermissionDenied("User cannot login")
 
 def create_user_hook(user_identity, target_user):
     """Automatically allow login for user created through SAML"""
     target_user.saml_login_enabled = True
     target_user.save()

Note: this should be mentioned in changelog, as it requires updating the signature of the hooks methods.