Compatibility with graphql-upload

[vulcanhoist-jdalpe]

Hi,

First, thanks for all the work you are doing for these libraries!

Its not much of an issue as it is a question following my transition from express-graphql to graphql-http. Express-graphql used to work with graphql-upload but now it seems to me that the handler is blocking my POST request with an image because the Content-Type is not "application/json".

Is this limitation is expected?

Thanks,

Expected Behaviour
I expect this library to accept multipart/form-data Content-Type.

Actual Behaviour
Right now, the library only accepts "application/json" as Content-Type for POST requests. Otherwise, it throws a 415 Unsupported Media Type