[review] Carrier config support and fwupd integration

[Aleksander Morgado]

Hey Dan & all,

The following MR adds support for reporting the current carrier config
in use, and also implements automatic carrier config switching based
on QMI PDC, initially done for the DW5821e.
https://gitlab.freedesktop.org/mobile-broadband/ModemManager/merge_requests/66

A single modem may have multiple per-carrier configurations stored,
and then we can select which one to use by default based on the
currently available SIM card. E.g. a modem running with a Verizon SIM
card will use the Verizon-specific configuration, and if the user
inserts an AT&T SIM card, ModemManager will detect it and
automatically switch to the AT&T-specific configuration.

This new carrier config logic also allows us to integrate
"carrier-specific upgrade paths" in fwupd. E.g. vendors may push to
fwupd firrmware updates for a given module that may apply to specific
operators only. This is quite common because each operator ends up
with specific firmware versions and configs tested and approved, and
so we may want to limit upgrading firmware only to those versions
approved in each carrier by default.

The integration of firmware update for ModemManager devices is
currently limited to those supporting fastboot and/or QMI PDC. E.g.
the DW5821e or some other Quectel devices.
https://github.com/hughsie/fwupd/pull/875

Comments welcome!

-- 
Aleksander
https://aleksander.es