Support for application/graphql content type

[vangapr]

Current spring boot graphql does not seem to support application/graphql content type with query text as body as specified here ( https://graphql.org/learn/serving-over-http ).

quote from the above specification:

In addition to the above, we recommend supporting two additional cases:

• If the "query" query string parameter is present (as in the GET example above), it should be parsed and handled in the same way as the HTTP GET case.
• If the "application/graphql" Content-Type header is present, treat the HTTP POST body contents as the GraphQL query string.

From GraphQlWebFluxAutoConfiguration.java:

RouterFunctions.Builder builder = RouterFunctions.route()
				.GET(graphQLPath, request ->
						ServerResponse.status(HttpStatus.METHOD_NOT_ALLOWED)
								.headers(headers -> headers.setAllow(Collections.singleton(HttpMethod.POST)))
								.build())
				.POST(graphQLPath,
						accept(MediaType.APPLICATION_JSON).and(contentType(MediaType.APPLICATION_JSON)),
						handler::handleRequest);

[bclozel]

The graphQL over HTTP is still being worked on and I think we're keeping things the way they are for now until progress is made (see #11 (comment)).

As for the content-type we're more likely to choose application/graphql+json as suggested in the spec.

[rstoyanchev]

After discussing this further, the spec draft now requires this and keeps application/json as a fallback for compatibility. We should make sure the server supports both and uses the one that's requested, while the client will use application/graph+json by default. The client changes are needed in Spring GraphQL while the server would also require a change in the Boot starter.