Push Suppression (Experimental Feature)

[tototomate123]

This PR adds an opt-in push suppression feature to cut down on mobile notifications when a user is actively using another client. It's currently marked as experimental and is disabled by default.

What's new

• Added config flag:
  suppress_push_when_active = true
• Presence service now tracks the timestamp of the last /sync per user in memory.
• /sync calls update that timestamp automatically.
• Push sender checks:
  • user is Online
  • last active < ~65 s
  • last sync gap < ~32 s
    => If all match, push delivery is suppressed; otherwise, notifications are sent as usual.

Why the heuristic?

Initially, I tried implementing this using presence alone, but that turned out to be too "sticky".
Presence keeps users marked as Online for ~5 minutes (default config) after they stop syncing, so mobile notifications stayed suppressed much longer than intended.

This update adds a simple heuristic based on the gap since the last /sync request. With this, push notifications resume after ~30 seconds of inactivity without changing presence idle timers or requiring extra presence updates.

Notes

• Fully opt-in, preserving legacy behavior by default.
• No schema or federation changes.
• If presence lookups fail, pushes are delivered as before.

Next steps / ideas?

• Make the thresholds configurable?
• Add metrics for suppressed vs delivered pushes?

[jevolk]

Sorry about the delay in getting to this but I am definitely excited about it. Thank you so much for making this effort 🙏🏻