The available methods are:
It takes as parameters: the user name and a dictionary of login parameters. It returns in case of success the user ID and the session. If the parameters are not valid to authenticate the user, it returns nothing. Otherwise if it misses a key in the parameters, it raises a LoginException exception with the missing key name, type and the message to ask to the user.
It takes no parameters and it invalidate the current session.
The authorization field is constructed by the username, the user ID and the session combined with a single colon and encoded in Base64. The session is retrieved by calling the method common.db.login.