Estructura inicial del proyecto

backend/node_modules/mongoose/lib/helpers/once.js

@@ -0,0 +1,12 @@
+'use strict';
+
+module.exports = function once(fn) {
+  let called = false;
+  return function() {
+    if (called) {
+      return;
+    }
+    called = true;
+    return fn.apply(null, arguments);
+  };
+};