fix(hydra): use correctly enable_docs

[alanpoulain]

Q	A
Branch?	4.1
Tickets	N/A
License	MIT
Doc PR	N/A

This PR aims to fix definitively a recurring issue: JSON-LD documentation is mandatory but users don't want to expose their endpoints when the API is private: #1568

The enable_docs configuration parameter removes the api_doc route: the documentation is not exposed anymore, but the URL is needed in some parts of the API Platform code: JSON-LD context, Hydra links, etc.
It regularly causes some bugs.

A relating PR was done in 2018:
#1731

This PR was removing the code adding the Hydra headers when the docs is disabled.
IMO @dunglas's comment was right:

IMO we must never disable the Hydra docs (or throw) when JSON-LD is enabled. The hydra "doc" is mandatory for JSON-LD (because we use Hydra types everywhere in JSON-LD documents) and Hydra compliance.

In 2023 another PRs were done but never merged:
#5676
#5862

@dunglas's comments were having the same point:

#5676 (comment)

No, contexts must always exist according to the JSON-LD spec.

IMHO we have two options:

• Always register the docs route but "manually" throw a NotFoundHttpException if enable_docs is set to false (consequently the route will technically exists in the Symfony router and the error will be prevented)
• Always generate the Hydra "docs" if JSON-LD is enabled, even if enable_docs is set to false (but continue to disable the OpenAPI endpoint, Swagger UI etc)

IMHO option 2 is more correct and easier to implement.

#5862 (comment)

I wonder if we cannot do that in a cleaner way: for instance, we could set docs_formats in the DI Extension to jsonld if enabled_docs is false, so we can simplify the routing part and always register the route, as it will work only for JSON-LD.

My proposal:

• Always enable the route.
• If enable_docs is set to false, only the jsonld documentation format is registered.
• Since the JSON-LD/Hydra documentation is always exposed, if enable_docs is false, hydra:supportedClass is not filled: the API resources are not included in the documentation but all the other keys stay (@context, @vocab...). To do this, it uses the new hideHydraOperation introduced in feat(metadata): hide an hydra endpoint #6871.
• Bonus: if the entrypoint is also disabled (enable_entrypoint set to false), the entrypoint is not added to hydra:entrypoint and hydra:supportedClass.