Add streaming service

Adds a service capable of streaming Any objects bi-directionally.
This can be used by services to send data, received data, or to
initiate requests from server to client.

Signed-off-by: Derek McGowan <derek@mcg.dev>

metadata/gc.go

@@ -46,6 +46,8 @@ const (
 	ResourceIngest
 	// resourceEnd is the end of specified resource types
 	resourceEnd
+	// ResourceStream specifies a stream
+	ResourceStream
 )
 
 const (