text: Title: Add "raw" endpoint to return raw, unparsed request data?
  Body: If possible, please consider adding a `/raw` or `/echo` endpoint that returns the raw HTTP request that the server received.  
  This feature can be used to help diagnose misbehaving applications (e.g. sending duplicate headers with different values or using incorrect line endings) or debug applications using niche HTTP features (e.g. sub-headers for `multipart/form-data` sections).