Add a Journald Logger

[agrare]

Adds a class enabling users to add entries into the journald log with a standard ruby Logger interface.

[Fryguy]

Nice! We just have to make sure this gem and MIQ will still "work" on non-journald systems

[carbonin]

Is this really not "A Thing" already?

I haven't looked very hard, but it seems like a very common use case.

Alternatively if we're running under systemd, could we log to stdout and have that captured by the journal?

[agrare]

Is this really not "A Thing" already?

Foreman has a logger (https://github.com/theforeman/journald-logger) but it uses a C extension (https://github.com/theforeman/journald-native) which requires the systemd devel headers, whereas this gem uses FFI (https://github.com/ledbettj/systemd-journal)

Alternatively if we're running under systemd, could we log to stdout and have that captured by the journal?

Yeah I considered that but this gives us control over the log severity which is helpful for using filtering with journalctl --priority=err

[agrare]

Okay @Fryguy this should be good to go