CommonResponseWriter is a wraper on top of extproc.CommonResponse It provides a fluent API to mutate the request and response headers and body.

ImmediateResponseWriter is a wraper on top of extproc.ProcessingResponse_ImmediateResponse.

RequestContext stores the context between the different gRPC messages received from Envoy and it is used to store the request headers, response headers, and other information about the request.