feat: Add setup check warning if instance is in debug mode

[juliusknorr]

I've seen a couple of instances running in debug mode in production recently and thought it might be a good idea to add a setup check for this since we only recommend it for development purposes as it may widen security measurements and also could introduce unexpected behaviour for regular users where the js assets are not automatically invalidated in the browser cache.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[solracsf]

as it may widen security measurements and also could introduce unexpected behaviour for regular users.

Maybe add it to the warning too?

[szaimen]

Good idea!