Implement a reverse proxy using grpc-gateway

proto/google/api/httpbody.proto

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+// Copyright 2018 Google LLC.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+syntax = "proto3";
+
+package google.api;
+
+import "google/protobuf/any.proto";
+
+option cc_enable_arenas = true;
+option go_package = "google.golang.org/genproto/googleapis/api/httpbody;httpbody";
+option java_multiple_files = true;
+option java_outer_classname = "HttpBodyProto";
+option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
+
+// Message that represents an arbitrary HTTP body. It should only be used for
+// payload formats that can't be represented as JSON, such as raw binary or
+// an HTML page.
+//
+//
+// This message can be used both in streaming and non-streaming API methods in
+// the request as well as the response.
+//
+// It can be used as a top-level request field, which is convenient if one
+// wants to extract parameters from either the URL or HTTP template into the
+// request fields and also want access to the raw HTTP body.
+//
+// Example:
+//
+//     message GetResourceRequest {
+//       // A unique request id.
+//       string request_id = 1;
+//
+//       // The raw HTTP body is bound to this field.
+//       google.api.HttpBody http_body = 2;
+//     }
+//
+//     service ResourceService {
+//       rpc GetResource(GetResourceRequest) returns (google.api.HttpBody);
+//       rpc UpdateResource(google.api.HttpBody) returns
+//       (google.protobuf.Empty);
+//     }
+//
+// Example with streaming methods:
+//
+//     service CaldavService {
+//       rpc GetCalendar(stream google.api.HttpBody)
+//         returns (stream google.api.HttpBody);
+//       rpc UpdateCalendar(stream google.api.HttpBody)
+//         returns (stream google.api.HttpBody);
+//     }
+//
+// Use of this type only changes how the request and response bodies are
+// handled, all other features will continue to work unchanged.
+message HttpBody {
+  // The HTTP Content-Type header value specifying the content type of the body.
+  string content_type = 1;
+
+  // The HTTP request/response body as raw binary.
+  bytes data = 2;
+
+  // Application specific response metadata. Must be set in the first response
+  // for streaming APIs.
+  repeated google.protobuf.Any extensions = 3;
+}