Contao: Cache tag invalidation

[leofeyer]

As discussed in https://github.com/contao/contao/pull/2103#issuecomment-671283944, we are currently always invalidating both the specific tag and the general "category" tag (e.g. contao.db.tl_news.61 and contao.db.tl_news), which kind of renders the specific tag useless. Maybe we can improve this?

[leofeyer]

We also need to discuss and fix this:

@ausi wrote: If you add a new news article the list module on the website will not be tagged with this new contao.db.tl_news.ID and therefore the new article would not show up. If we invalidate the parent contao.db.tl_news_archive.ID (as we did before this PR) the news list module would show the new article as soon as it was published.

@Toflar wrote: But that's only "by chance". It only works if there is a parent table. If there's not, it wouldn't work. We need special handling for "create".

[leofeyer]

As discussed in Mumble on August 27th, these tags should be set for e.g. a news item:

• news reader: tl_news.61, tl_content.11
• news list: tl_news_archive.1, tl_news.61, tl_news.62, tl_content.11, tl_content.12

Then:

• Case 1: A news archive is created /edited/unpublished/resorted/removed -> invalidate tl_news_archive, tl_news_archive.1, tl_news.61, tl_news.62, tl_content.11, tl_content.12
• Case 2: A news item is created/edited/unpublished/resorted/removed -> invalidate tl_news_archive, tl_news_archive.1, tl_news.61, tl_content.11

So all parent and child IDs need to be invalidated. Only the top parent record gets a general tag without ID.

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