Response content type

[calacaly]

Can we support more response content type.

This library is very user-friendly, but recently encountered response content types that seem to be unsupported, which is a bit imperfect

• application/hal+json

none of producers: map[application/json:0x783ea0 application/octet-stream:0x762da0 application/x-yaml:0x783d60 application/xml:0x783f20 text/csv:0x7654c0 text/html:0x784420 text/plain:0x783fa0] registered. try application/hal+json

• application/vnd.error+json
  This is probably not supported either

[fredbi]

@calacaly

The way to add non-default producers (or consumers) is to register them.
If you use an untyped API, you may see how this is done here: ./middleware/untyped/api_test.go
If you generate a typed API, you may take a look at this example : https://github.com/go-swagger/go-swagger/blob/0477d4a3af47ac446ab3d5d357ab36c03c117b93/examples/generated/restapi/operations/petstore_api.go#L419

Essentially, the API interface exposes a "ProducerFor(mime) runtime.Producer" method that resolves the mime to the appropriate producer.