[FAU-441] feat: update modified value if any of degree program properties were updated

[shvlv]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes/features)
• Docs have been added/updated (for bug fixes/features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
Feature.

What is the current behavior? (You can also link to an open issue here)
https://inpsyde.atlassian.net/browse/FAU-441

What is the new behavior (if this is a feature change)?
I wouldn't say I like the coupling of the new functionality with the cache module, but now the cache module is the single place where we have all hooks triggered for any degree program data changes. Decoupling the functionality is a huge and dangerous refactoring effort. Anyway, we already have a cache module coupled with revision functionality and the degree program output plugin can't work without a cache at all (at least for degree program overviews). So our "cache" is not a secondary but a core functionality now 🤷‍♂️ .

The same is true for extracting helper repositories. We have many domain-related repositories, so creating new repositories just to wrap the get_posts invocation doesn't make much sense.

Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
No.

Other information:

[tyrann0us]

Thank you for working on this! LGTM.
What do you think of adding @wp-hooks to the updateModifiedDate callback, maybe even to all caching-related add_action callbacks according to the Boy Scout rules?

[amiut]

Thank you

[shvlv]

What do you think of adding @wp-hooks to the updateModifiedDate callback, maybe even to all caching-related add_action callbacks according to the Boy Scout rules?

I've just tried, but I'm not sure it adds clarity 😄

For our custom event handlers, we get the event object as a param, so it's self-explanatory - public function updateModifiedDate(CacheInvalidated $event): void. We have dynamic events for WordPress events, and update_option_{$prefixedOption} and edited_{$key} are not helpful. WhenDegreeProgramTermUpdated::invalidateCache is used in different contexts.

Maybe we can stay it as is.