Changes to POST /feedback_portal/:portalId/plain_feedback

added the new optional request property anonymous

added the new optional request property attachmentIds

added the new optional request property issuer

added the new optional request property sourceUrl

added the new optional request property submitterId

added the new optional request property submitterName

added the new optional request property widgetId

added the non-success response with the status 503

added the optional property error to the response with the 401 status

added the optional property error to the response with the 403 status

added the optional property error to the response with the 500 status