Add custom header support for HTTP proxy

infra/conf/http.go

@@ -53,6 +53,7 @@ type HTTPRemoteConfig struct {
 
 type HTTPClientConfig struct {
 	Servers []*HTTPRemoteConfig `json:"servers"`
+	Headers map[string]string   `json:"headers"`
 }
 
 func (v *HTTPClientConfig) Build() (proto.Message, error) {
@@ -77,5 +78,12 @@ func (v *HTTPClientConfig) Build() (proto.Message, error) {
 		}
 		config.Server[idx] = server
 	}
+	config.Header = make([]*http.Header, 0, 32)
+	for key, value := range v.Headers {
+		config.Header = append(config.Header, &http.Header{
+			Key:   key,
+			Value: value,
+		})
+	}
 	return config, nil
 }