Code review comment for ~ec0/charm-nagios:readonly-account

In this case, we're already managing a chunk of the config files and I don't see an alternative for that particular config (no conf.d option for cgi.cfg).

While we could use a sed equivalent to alter the config on that one file, we don't take that approach with nagios.cfg and I'd rather take a consistent approach. If this was a fresh charm we could argue otherwise. Any new config options that package updates add to that file _SHOULD_ have sensible defaults built in and not require setting at all, if we wish to add config items for those settings later then we'd need to modify the charm anyway.

I've tested this change and find it to be working well, and we have multiple customers that are affected by the change not getting merged.