chore: API documentation updates for CSAT surveys (#7255)

- Expose conversation uuid in APIs
- swagger documentation for cast survey update via public/message/update endpoints
- swagger documentation for survey/responses/conversation_uuid endpoint

Fixes: #6328

app/views/api/v1/models/_conversation.json.jbuilder

@@ -1,4 +1,5 @@
 json.id conversation.display_id
+json.uuid conversation.uuid
 json.created_at conversation.created_at.to_i
 json.contact do
   json.id conversation.contact.id