Implicit CloudTrail trail dependency

[mschweitzer-sd]

This is maybe more of a documentation issue?

I was trying to debug why new log groups weren't having their retention set by cloudwatch-logs-auto-set-retention until I debugged it to the lack of a CloudTrail trail capturing management events (write events specifically). I imagine cloudwatch-logs-auto-subscribe has the same dependency.

I think this should be called out in the docs for both apps, otherwise it just seems like things aren't working.

...Almost forgot to mention, thanks for writing these! They are super helpful and really feel like they should be built into AWS somehow.

It's possible the ergonomics of these apps could be slightly improved by creating a trail if one isn't supplied or something. Just tossing out the idea there...probably not worth the overhead of having another trail in the account when an existing trail can do the job just fine.