[RFC] New 'ConnectionError' property in the Bearer objects

[Aleksander Morgado]

Hey Dan & all,

I've been thinking in upgrading the Bearer object DBus API with a new
"ConnectionError" property that would include (if known) the reason
why a given bearer is disconnected (either due to a failed connection
attempt, a network-initiated disconnection, or any other failure that
would trigger the disconnection).

Please see the following merge request for context and some examples:
https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/merge_requests/533

The merge request also includes a bunch of improvements regarding to
error handling inside the MM daemon; like updated mobile equipment
errors per the latest 3GPP specs or improved QMI/MBIM error mappings
to those mobile equipment errors.

Comments and reviews welcome!

-- 
Aleksander
https://aleksander.es