code: func (wfe *WebFrontEndImpl) validPOSTAsGETForAccount(
  	request *http.Request,
  	ctx context.Context,
  	logEvent *web.RequestEvent) (*core.Registration, *probs.ProblemDetails) {
  	// Call validPOSTForAccount to verify the JWS and extract the body.
  	body, _, reg, prob := wfe.validPOSTForAccount(request, ctx, logEvent)
  	if prob != nil {
  		return nil, prob
  	}
  	// Verify the POST-as-GET payload is empty
  	if string(body) != "" {
  		return nil, probs.Malformed("POST-as-GET requests must have an empty payload")
  	}
  	return reg, prob
  }
docs: // validPOSTAsGETForAccount checks that a given POST request is valid using
  // `validPOSTForAccount`. It additionally validates that the JWS request payload
  // is empty, indicating that it is a POST-as-GET request per ACME draft 15+
  // section 6.3 "GET and POST-as-GET requests". If a non empty payload is
  // provided in the JWS the invalidPOSTAsGETErr problem is returned. This
  // function is useful only for endpoints that do not need to handle both POSTs
  // with a body and POST-as-GET requests (e.g. Order, Certificate).