Clarify the use of Content Negotiation and the `f` query expectations

Detail

While browsing the OGC API - Processes - Part 1: Core draft, I noticed that the ?f= query is not that well-defined in terms of expected requirements.

There are some examples using it, such as the 7.2.2. Response - Landing Page Example or 7.10.2. Response - Process List Example 2.
There are also some mentions in the extra note under 7.3.2. Retrieve an API definition - Response and 10. Requirements classes for encodings.

However, beside those, it is not really indicated explicitly (a permission or recommendation) that it may be supported.

Also, there are not many cross-links applied when mentioning "content negotiation" in general in some descriptions, so one as to somewhat land on these notes by chance to be aware of them.

Furthermore, 10. Requirements classes for encodings (which could also be better cross-linked when mentioning "Content Negotiation" across the text) mostly refers to:

• https://datatracker.ietf.org/doc/html/rfc2616#section-12
• https://www.rfc-editor.org/rfc/rfc9110.html#name-content-negotiation-fields

Both of these references are mostly referring to Accept, Accept-Encoding, Accept-Language, etc. Therefore, it is still not that obvious that ?f= could apply as well, or that 7.7. Content negotiation by profile might also be involved.

In certain cases, like for 7.3.2. Retrieve an API definition - Response, the plain text "content negotiation" without any cross-reference might actually be misleading since Accept, etc. are not obviously indicated, and the note just after it quickly highlights the (IMO, less-preferred than header) alternatives using a file extension or accept/f queries.

Actions

I recommend:

• adding cross-references explicitly to 10. Requirements classes for encodings anywhere "content negotiation" is mentioned
• adding an explicit recommendation or permission about ?f= somewhere under 10. Requirements classes for encodings
• adding a cross-reference to the above ?f= item when mentioning such alternatives