Add a section about the HTTP protocol

[martinbonnin]

The current spec mentions HTTP 1.1 everywhere so I guess this is a requirement? But we might want to allow HTTP 2.0 still?

[benjie]

The current spec mentions HTTP 1.1 everywhere

I searched for 1.1 in the spec and I found a single hit - the part that governs what to do if no Accept header is provided. Am I missing other positions?

In alignment with the HTTP 1.1 Accept
specification, when a client does not include at least one supported media type
in the Accept HTTP header, the server MUST either:

1. Respond with a 406 Not Acceptable status code and stop processing the
   request (RECOMMENDED); OR
2. Disregard the Accept header and respond with the server's choice of media
   type (NOT RECOMMENDED).

My interpretation of this (and to be fair it looks like I may have been the person who wrote it, so I'm not impartial), it's saying "here's what to do if there's no Accept, which follows the conventions laid out by HTTP1.1's definition of Accept". I don't think it's requiring the use of HTTP 1.1 at all?

[benjie]

I'm not convinced that we should require support for HTTP1.1. Is there a good reason that servers should not be able to be HTTP2+ only?

[martinbonnin]

https://graphql.github.io/graphql-over-http/draft/#sel-DANFCAACCB_9Z

A server must comply with [RFC7231](https://datatracker.ietf.org/doc/html/rfc7231).

And RFC7231 starts with "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content". I didn't read the whole RFC so maybe it's just about semantics but it wasn't immediatly clear that HTTP 2 was supported.

I'm not convinced that we should require support for HTTP1.1. Is there a good reason that servers should not be able to be HTTP2+ only?

I also think we should allow HTTP2+ only. Maybe it's just a clarifying sentence that

A server MUST comply with RFC7231 semantics. 

A server MUST support at least one version of HTTP message format, such as 1.1 or 2.0 as long
as the RFC7231 semantics are observed. 

It is recommended that a server supports several versions of the HTTP message format for wider
compatibility.

Or something like this?