- Condition type = groupchat is not needed because we drop messages
type groupchat that come from the user archive. To get these messages
we will query the MUC.
- Because of this the logging method save_if_not_exists() can be much
simpler
- Refactor and clean up code around MamMessageReceivedEvent
- Goal is to add a GcMamMessageReceivedEvent later on
- For that cause added a raw-mam-message-received base event