config-editor doesn't detect broken config

[taukakao]

If you create an invalid config, abroot config-editor will save it anyway and will not be able to run again to fix the issue.

[mirkobrombin]

A built-in editor is probably the best solution here, so we validate it before saving.

[taukakao]

@mirkobrombin
I think a built-in editor would be overkill.
We could alternatively copy the file somewhere in /tmp, edit it there and validate it before writing it back to /etc/abroot

[mirkobrombin]

I would define it as "overkill" but complex. Anyway your idea is better.