Use generated interface

cmd/web/helpers.go

@@ -19,6 +19,15 @@ func (app *application) serverError(w http.ResponseWriter, r *http.Request, err
 	json.NewEncoder(w).Encode(response)
 }
 
+func (app *application) badRequestError(w http.ResponseWriter, r *http.Request, err error) {
+	w.WriteHeader(http.StatusBadRequest)
+	var response = api.ErrorResponse{
+		Code:    http.StatusBadRequest,
+		Message: err.Error(),
+	}
+	json.NewEncoder(w).Encode(response)
+}
+
 func (app *application) clientError(w http.ResponseWriter, status int, message string) {
 	w.WriteHeader(status)
 	var response = api.ErrorResponse{