Uploads a recording file and attaches it to the conversation. The request is a multipart/form-data body with exactly two parts:
- params - a single text part whose value is a JSON document with projectId and conversationId. Do not split the fields into separate parts such as params[projectId] and params[conversationId] - such a request is rejected with 400 "Multipart type doesn't have 'params' part".
- the recording file - a file part with one of the supported audio content types: audio/mpeg, audio/wav, audio/x-wav, audio/ogg. The file part is matched by its Content-Type, so its name (recordingFile below) is not significant.
Example request:

POST /recording/upload HTTP/1.1
Content-Type: multipart/form-data; boundary=boundary

--boundary
Content-Disposition: form-data; name="params"

{"projectId":"e12bdeca-a99c-480c-89e1-e26b2f3f76b7","conversationId":"43578954378959789875"}
--boundary
Content-Disposition: form-data; name="recordingFile"; filename="recording.mp3"
Content-Type: audio/mpeg

<binary audio data>
--boundary--