The authenticators should have a similar way to print diagnostic
information as filter and routers do. This allows the authenticators to
print the users in their own format.
In the future, all the diagnostic entry points should be changed so that
they return a structure that contains the information in a standard
form. This information can then be formatted in different ways by other
modules.
Currently the only situation where a user needs to be authenticated after
the initial authentication is when a COM_CHANGE_USER is being
executed. This was previously handled by directly calling a function in
the MySQLAuth authenticator.
The new entry in the API of the authenticators is very specific to MySQL
and should be reviewed once other protocols are added.
