Introduce GraphQL-over-HTTP response

[martinbonnin]

Just like there is GraphQL-over-HTTP request, this PR introduces GraphQL-over-HTTP response.

Using GraphQL response was misleading because the HTTP specification doesn't say anything about response streams and we might end up using a separate media type for this (application/graphql-responses+jsonl, ...)

Instead, this PR introduces a new GraphQL-over-HTTP response that is either an execution result or a request error result, but not a response stream.

[benjie]

@martinbonnin as agreed at the GraphQL-over-HTTP working group, I've updated this to lean heavily on the GraphQL spec to define the result shapes, rather than redefining them here. I've also fixed outdated references to terms in the spec that have since been refined - it wasn't just "GraphQL response" that was out of date (as you rightly caught!), but also "field error" has been replaced with "execution error" and the section links were also broken due to capitalization differences. I've moved to linking to the term definitions instead of section headers as I believe these links will be more stable. I've linked to the Sept 2025 main spec release right now, but if we can get a Sept 2026 release ready before this goes out I'll update the reference so they can go out either together or slightly staggered (HTTP following main spec) - that can be done in a follow up to this PR.

Please take a look and let me know what you think.

[martinbonnin]

@benjie I can't approve my own PR but LGTM!

[martinbonnin]

Was this meant to be commited? Do we have a release already? 👀

[benjie]

Wrong year, Martin!

I've linked to the Sept 2025 main spec release right now, but if we can get a Sept 2026 release ready before this goes out I'll update the reference so they can go out either together or slightly staggered (HTTP following main spec) - that can be done in a follow up to this PR.

[martinbonnin]

😂 What a year, huh?

Sounds good 👍 Thanks!