bridge.history_sync.max_initial_conversations:
This setting determines the maximum number of initial conversations
that should be backfilled. The data for all the other conversations
will be stored in the database for backfill at a later time.
bridge.history_sync.immediate:
These settings are for the initial backfill that should be performed
to populate each of the initial chats with a few messages so that
users can continue their conversations without loosing context.
bridge.history_sync.deferred:
These settings are for backfilling the rest of the chat history that
was not covered by the immediate backfills. These should generally be
done at a slower pace to avoid overloading the homeserver.
