feat(auth): implement user authentication system

backend/node_modules/generate-function/example.js

@@ -0,0 +1,27 @@
+const genfun = require('./')
+const { d } = genfun.formats
+
+function multiply (a, b) {
+  return a * b
+}
+
+function addAndMultiplyNumber (val) {
+  const fn = genfun(`
+    function (n) {
+      if (typeof n !== 'number') {
+        throw new Error('argument should be a number')
+      }
+      const result = multiply(${d(val)}, n + ${d(val)})
+      return result
+    }
+  `)
+
+  // use fn.toString() if you want to see the generated source
+
+  return fn.toFunction({multiply})
+}
+
+const addAndMultiply2 = addAndMultiplyNumber(2)
+
+console.log(addAndMultiply2.toString())
+console.log('(3 + 2) * 2 =', addAndMultiply2(3))