docs: add guide on graphql-http errors

[sarahxsanders]

Description

• Adds guide on graphql-http errors (just some common ones) and how to debug them
• Adds block on Best Practices landing page

Feel free to suggest additional common errors if there are any that might be important to highlight here!

[vercel]

@sarahxsanders is attempting to deploy a commit to the The GraphQL Foundation Team on Vercel.

A member of the Team first needs to authorize it.

[benjie]

This is really good general reference that should be applicable to any server implementing GraphQL-over-HTTP (not just the reference implementation).

One concern is it does not incorporate the application/graphql-response+json media type. Since the spec is currently a draft I wouldn't normally be too concerned, except we do link to the spec so we should recommend its recommendations.

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
graphql-github-io	❌ Failed (Inspect)			Jun 7, 2025 4:57am

[sarahxsanders]

This is really good general reference that should be applicable to any server implementing GraphQL-over-HTTP (not just the reference implementation).

One concern is it does not incorporate the application/graphql-response+json media type. Since the spec is currently a draft I wouldn't normally be too concerned, except we do link to the spec so we should recommend its recommendations.

added a section about understanding response formats, I hope that addresses this better!

[enisdenjo]

Are we sure about the 415 and 422? The spec itself does not recommend them, it's up to the implementor to choose using it and follow HTTP conventions.

[sarahxsanders]

@enisdenjo I removed those sections and added a section w/ a disclaimer, let me know if this addresses that!

[enisdenjo]

It's looking good now, thanks!