feat(auth): implement user authentication system

backend/node_modules/async/internal/onlyOnce.js

@@ -0,0 +1,15 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+exports.default = onlyOnce;
+function onlyOnce(fn) {
+    return function (...args) {
+        if (fn === null) throw new Error("Callback was already called.");
+        var callFn = fn;
+        fn = null;
+        callFn.apply(this, args);
+    };
+}
+module.exports = exports.default;