Add timing metrics for audio input to handler in speech service (#181)

# Description
Handles `client_sent` timestamp and calculates how long it took for the
message to be handled in this module

# Issues
<!-- If this is related to or closes an issue/other PR, please note them
here -->

# Other Notes
NeonGeckoCom/neon_audio#154

Co-authored-by: Daniel McKnight <[email protected]>

neon_speech/service.py

@@ -375,6 +375,9 @@ def build_context(msg: Message):
                               'transcribed': time()}}
             return ctx
 
+        received_time = time()
+        sent_time = message.context.get("timing", {}).get("client_sent",
+                                                          received_time)
         ident = message.context.get("ident") or "neon.audio_input.response"
         LOG.info(f"Handling audio input: {ident}")
         if message.data.get("audio_data"):
@@ -385,10 +388,13 @@ def build_context(msg: Message):
         lang = message.data.get("lang")
         try:
             with self._stopwatch:
+                # _=transformed audio_data
                 _, parser_data, transcriptions = \
                     self._get_stt_from_file(wav_file_path, lang)
             message.context["audio_parser_data"] = parser_data
             context = build_context(message)
+            if received_time != sent_time:
+                context['timing']['mq_from_client'] = received_time - sent_time
             context['timing']['get_stt'] = self._stopwatch.time
             data = {
                 "utterances": transcriptions,