Configure response content type at the method level

[nboukeffa]

This PR will add the possibility to configure the response content
type at the method level.

To do such the developer will have to set the produces property
like in the following example.

rpc OverwriteResponseContentType(google.protobuf.Empty) returns (google.protobuf.StringValue) {
	option (google.api.http) = {
		get: "/v2/example/overwriteresponsecontenttype"
	};
	option (grpc.gateway.protoc_gen_swagger.options.openapiv2_operation) = {
		produces: "application/text"
	};
}

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[nboukeffa]

@googlebot I signed it!

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[nboukeffa]

I'm not sure why the build is failing on Circle CI. It's passing locally. If someone can help...

[johanbrandhorst]

The bazel failure should be fixed by running:

$ docker run -itv $(pwd):/grpc-gateway -w /grpc-gateway --entrypoint /bin/bash --rm \
    l.gcr.io/google/bazel -c 'bazel run :gazelle'

From https://github.com/grpc-ecosystem/grpc-gateway/blob/master/CONTRIBUTING.md

[johanbrandhorst]

LGTM, lets just get the bazel error fixed (I think it's the new wrappers import in a_bit_of_everything.proto that's causing it).

[codecov-io]

Codecov Report

Merging #1130 into master will decrease coverage by 0.06%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master   #1130      +/-   ##
=========================================
- Coverage   53.87%   53.8%   -0.07%     
=========================================
  Files          42      42              
  Lines        4197    4202       +5     
=========================================
  Hits         2261    2261              
- Misses       1689    1693       +4     
- Partials      247     248       +1

Impacted Files	Coverage Δ
protoc-gen-swagger/genswagger/types.go	0% <ø> (ø)	⬆️
examples/server/a_bit_of_everything.go	0% <0%> (ø)	⬆️
protoc-gen-swagger/genswagger/template.go	56.72% <0%> (-0.16%)	⬇️

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[johanbrandhorst]

Thanks for your contribution!

[nboukeffa]

All green. You were right the import was missing in the build definition. Your command did the trick.

Maybe adding it to the CONTRIBUTING.md could help.