Backend Plugins: Support handling of streaming resource response (#22580)

Use v0.19.0 of SDK.
Support handling of streaming resource response.
Disable gzip/compression middleware for resources 
to allow chunked/streaming response to clients the gzip
middleware had to be disabled since it buffers the full
response before sending it to the client.

Closes #22569

Co-Authored-By: Arve Knudsen <arve.knudsen@gmail.com>

pkg/plugins/backendplugin/contracts.go

@@ -37,8 +37,8 @@ func (hs HealthStatus) String() string {
 
 // CheckHealthResult check health result.
 type CheckHealthResult struct {
-	Status HealthStatus
-	Info   string
+	Status  HealthStatus
+	Message string
 }
 
 func checkHealthResultFromProto(protoResp *pluginv2.CheckHealth_Response) *CheckHealthResult {
@@ -51,8 +51,8 @@ func checkHealthResultFromProto(protoResp *pluginv2.CheckHealth_Response) *Check
 	}
 
 	return &CheckHealthResult{
-		Status: status,
-		Info:   protoResp.Info,
+		Status:  status,
+		Message: protoResp.Message,
 	}
 }
 
@@ -91,3 +91,46 @@ type CallResourceResult struct {
 	Headers map[string][]string
 	Body    []byte
 }
+
+type callResourceResultStream interface {
+	Recv() (*CallResourceResult, error)
+	Close() error
+}
+
+type callResourceResultStreamImpl struct {
+	stream pluginv2.Core_CallResourceClient
+}
+
+func (s *callResourceResultStreamImpl) Recv() (*CallResourceResult, error) {
+	protoResp, err := s.stream.Recv()
+	if err != nil {
+		return nil, err
+	}
+
+	respHeaders := map[string][]string{}
+	for key, values := range protoResp.Headers {
+		respHeaders[key] = values.Values
+	}
+
+	return &CallResourceResult{
+		Headers: respHeaders,
+		Body:    protoResp.Body,
+		Status:  int(protoResp.Code),
+	}, nil
+}
+
+func (s *callResourceResultStreamImpl) Close() error {
+	return s.stream.CloseSend()
+}
+
+type singleCallResourceResult struct {
+	result *CallResourceResult
+}
+
+func (s *singleCallResourceResult) Recv() (*CallResourceResult, error) {
+	return s.result, nil
+}
+
+func (s *singleCallResourceResult) Close() error {
+	return nil
+}