Minimum version: Midgard 1.4 (Bifrost)
When called the authentication credentials will be set to the state mod_midgard initially set them to. You can use this to temporarily become another user by calling mgd_auth_midgard, then mgd_unsetuid. Note that this is not a general 'undo' feature for mgd_auth_midgard since it sets the credentials to the initial state no matter how many times mgd_auth_midgard was called.