resolves issue #669

[infiton]

This issue resolves #669

Based on https://shopify.dev/changelog/graphql-over-http:

For requests to 2025-01 versions and after:

Use the /graphql endpoint. Using /graphql.json will automatically respond with application/json as it does now.
The request body must contain a [spec JSON encoding](https://graphql.github.io/graphql-over-http/draft/#sec-JSON-Encoding).
The Content-Type header must specify application/json. The legacy application/graphql request format is no longer supported. Requests with no supported content type will receive a 415 Unsupported Media Type response.
The Accept header now supports application/graphql-response+json and/or application/json response formats. Requests with no supported accept types will receive a 406 Not Acceptable response.

This change is backwards compatible as old api versions accept json requests like this

[infiton]

@lpinca any thoughts on this?

[lpinca]

Thank you.

[coveralls]

coverage: 100.0%. remained the same
when pulling ffa4cd1 on infiton:bug-fix-issue-669
into 48e23de on MONEI:master.