In order to improve the latency of Sync, we proposed to send push notifications to the clients in the same account.
Let's start simple and do client-driven push notifications after each Sync.
We could probably do better in the future but this is a fast and easy way to validate if the sync clients behavior is still consistent after this change.
For starters, let's send this notification only for the tabs and the clients collections, which are less prone to conflicts.

We already have a push payload definition for collectionChanged push message.

The endpoint path is pretty verbose, but I'd like to avoid using a generic /devices/notify endpoint and ending up with the same body as the push payloads. I'm open to suggestions.

cc @MarkH @rnewman @rfk @ckarlof @kitcambridge @vladikoff