Support more return codes

[m3nu]

Borg will get more detailed return codes to enhance error reporting. Likely in 1.2.x or 1.3 at the latest. Initial list here: https://github.com/borgbackup/borg/issues/6756#issuecomment-1147355783

This isn't breaking for us, since we only use 0, 1 and 2 at the moment. But we could use it to provide more detail to replace parsing full logs. Tasks in detail:

• [ ] Add feature check in borg_compat.
• [ ] Identify places that could benefit from getting a precise failure reason
• [ ] Implement new status messages, alerts, etc.

[Ananadharajan]

Though I'm new to oss, I would like to make contributions that would have long lasting and significant impact on the community.

Open to any advice !