* Ensure IMAP service sync cancel request waits until the sync has
completely cancelled rather than just signaling. It's possible that
due the context reset on `group.Cancel` that something may have not
have been bookmarked correctly in subsequent sync restarts.
* Handle connection lost/restored events in the services. Removes the
need to lock bridge users. Which could conflict with other ongoing
lock operations. Additionally, it ensure that if one service is
blocked it doesn't block the entire bridge.
* Revise access to bridge user locks.
The IMAP service no longer blocks the event loop from progressing. When
syncing the event loop continues as usual, allow other parts of the
bridge to continue updating.
Once the sync is complete, it resets the event id back to the last
handled id before sync started and then we play catch up.
Add two separate toggles to control event loop pausing. This is required
to prevent cases where the bridge requests the event loop to be paused
but a sync process completes and resumes the event loop.
For the loop to resume now both states need to be set to false. This
will be removed once GODT-2848 is implemented.
Wait for the current event poll to finish publishing events after a
request to pause the event loop. This is required to change the gluon
cache directory.
Rather than having the services subscribe to each individual event type,
have only one subscriber for the whole event object. This spreads the
logic to the service through the `EventHandler` type.
This is important for the next stage where the IMAP service will be
required to apply events from the past.
This patch adds the User Event Service which is meant to replace the
current event polling flow.
Each user interested in receiving events should register a new
subscriber using the `Service.Subscribe` function and then react on
the incoming events.
The current patch does not hook this up Bridge user as there are no
existing consumers, but it does provide extensive testing for the
expected behavior.
