Make log levels configurable?

[shajia-deshaw]

I've been trying to debug an error when doing differential backups but the only log statements I see is

WARN: local-1 process terminated unexpectedly on signal 11
...
WARN: unable to wait on child process: [10] No child processes

which is not very helpful.

I also noticed the log opts are hard-coded (https://github.com/operasoftware/cnpg-plugin-pgbackrest/blob/main/internal/pgbackrest/command/commandbuilder.go#L242-L258). Can we make this configurable? (Happy to contribute as usual)

[shajia-deshaw]

(cc: @Agalin)

[Agalin]

I'm not 100% sure right now as it was configured quite a while ago, but I believe there are some cases where pgbackrest no longer returns a valid JSON for some commands, or, to be more precise, it doesn't return only valid JSON. Might not be as easy to run it in debug log mode. Definitely should support at least configuring a redirect of debug logs to a file though.

I think a good thing to consider might be inverting the additional args logic - currently plugin's hardcoded values win (as is the case in the barman plugin) but I think being able to override any plugin-provided flag might actually be a feature. Also I'd need to check if it's valid to use reset flags here (--log-level-stderr=warn --reset-log-level-stderr --log-level-stderr=debug).

BTW I understand that the issue is about improved debugability, I just want to confirm that we're using diff backups in some of our environments just fine.