Support for dispatchers reporting connection/disconnection events
This allows users or packages to include custom scripts under /etc/ModemManager/connection.d (for users) or /usr/lib/ModemManager/connection.d (for packages) so that they are executed whenever bearers are connected or disconnected.
The scripts will receive 4 arguments:
- Modem DBus path
- Bearer DBus path
- Data interface name
- Status string: "connected" or "disconnected"
This will help us solve https://github.com/openwrt/openwrt/issues/8368