Purpose: Generate and send the response to the client.
A Service SAF is only called if each of the optional parameters type, method, and query specified in the directive in obj.conf match the request.
Remove existing content-type from rq->srvhdrs. Insert correct content-type in rq->srvhdrs.
Create any other headers in rq->srvhdrs.
Call protocol_status to set HTTP response status.
Call protocol_start_response to send HTTP response and headers.
Generate and send data to the client using net_write.
Return REQ_PROCEED if successful, REQ_EXIT on write error, REQ_ABORTED on other failures.