#697 Setup check for the HaRP container's version

[bnw]

Hi there,
I would like to help with this ticket.
This is my first contribution to Nextcloud, so I might need some pointers :)

Some open questions I already have:

1. I'm using the built-in version-compare. I'm guessing the HaRP version schema follows the PHP version string formatting closely enough for now. Do you have any concerns about this?
2. I set the MINIMUM_HARP_VERSION to the current HaRP version 0.3. Is this appropriate?
3. I'm caching the HaRP version checks for a week to keep the setup warnings page snappy. I'm using crc32 to quickly hash the HaRP settings into a cache key. I'm not familiar with the Entity system. Is there maybe a more elegant way to hash an Entity or even attach cache values to it directly?
4. Do you think there should be more infos (maybe in the docs) than what the warning messages give?
5. I wasn't sure how to add tests for this. I also couldn't find any tests for the already existing SetupCheck (DaemonCheck). If you think it is necessary to add tests, could you give me some pointers on how to set this up?
6. Do I need to update the translation files manually? Or is there some script to update them automatically? If yes, could you point me to it?

Thanks a lot and let me know if you require any changes :)