Move the info keys list added to user_authentication_* to a -define()
Use rabbit_misc:format/2 instead of lists:flatten/1 + io_lib:format/2
Use list comprehension instead of lists:foldl/3

To keep a somewhat logical order in the list of user_authentication_*
properties, reverse the order of the AUTH_NOTIFICATION_INFO_KEYS list.
This list was previously reversed by lists:foldl/3.
Only include ssl/certificate informations when the connection is over SSL

This gives lighter notifications for plain TCP connections.
Pass "extra properties" to notify_auth_result/{3,4} instead of a message

This avoids to passs an empty message in the case of successful
authentication.