Add validation, formatter & some configs

helpers/formatter.js

@@ -0,0 +1,20 @@
+const phoneNumberFormatter = function(number) {
+  // 1. Menghilangkan karakter selain angka
+  let formatted = number.replace(/\D/g, '');
+
+  // 2. Menghilangkan angka 0 di depan (prefix)
+  //    Kemudian diganti dengan 62
+  if (formatted.startsWith('0')) {
+    formatted = '62' + formatted.substr(1);
+  }
+
+  if (!formatted.endsWith('@c.us')) {
+    formatted += '@c.us';
+  }
+
+  return formatted;
+}
+
+module.exports = {
+  phoneNumberFormatter
+}