Extend the notification system to include member leave, kick and ban events,
mirroring the existing join notification functionality.
### Changes
- Added `_handle_leave_notifications` to process LEAVE, KICK and BAN events
- Integrated new notifications into existing membership event handlers
- Introduced `{actor}` placeholder with Matrix URI pill support
- Added `{actor_display}` as plaintext fallback
- Extended template renderer to support actor context
- Ensured consistent rendering across plaintext and HTML messages
- Added template cleanup for cases without an actor (e.g. voluntary leave)
### Templates
New placeholders:
- `{actor}` → clickable Matrix user pill
- `{actor_display}` → plain display name
### Configuration
New config keys:
- `leave_notification_message`
- `kick_notification_message`
- `ban_notification_message`
### Notes
- Fully async and non-blocking implementation
- Backwards compatible with existing templates
- No impact on join notification logic
- Scoped to rooms within configured space
Dome
0ee5f4cb1b