glib requires G_LOG_DOMAIN defined so that log messages are labeled
to belong to NetworkManager or libnm.
However, we don't actually want to use glib logging. Our library libnm
MUST not log anything, because it spams the user's stdout/stderr.
Instead, a library must report notable events via its API. Note that
there is also LIBNM_CLIENT_DEBUG to explicitly enable debug logging,
but that doesn't use glib logging either.
Also, the daemon does not use glib logging instead it logs to syslog.
When run with `--debug`.
Hence, it's not useful for us to define different G_LOG_DOMAIN per
library/application, because none of our libraries/applications should
use glib logging.
It also gets slightly confusing, because we have the static library like
`src/libnm-core-impl`, which is both linked into `libnm` (the library)
and `NetworkManager` (the daemon). Which logging domain should they use?
Set the G_LOG_DOMAIN to "nm" everywhere. But no longer do it via `-D`
arguments to the compiler.
See-also: https://developer.gnome.org/glib/stable/glib-Message-Logging.html#G-LOG-DOMAIN:CAPS
We want to move platform code to "shared/nm-platform". However, platform
code uses the logging infrastructure from the daemon, there is thus
an odd circular dependency.
Solve that by moving the "src/nm-logging.[hc]" to a new helper library
in "shared/nm-log-core".
NetworkManager core is huge. We should try to split out
parts that are independent.
Platform code is already mostly independent. But due to having it
under "src/", there is no strict separation/layering which determines
the parts that can work independently. So, while the code is mostly
independent (in practice), that is not obvious from looking at the
source tree. It thus still contributes to cognitive load.
Add a shared library "shared/nm-platform", which should have no
dependencies on libnm-core or NetworkManager core.
In a first step, move the netlink code there. More should follow.
