🚩 (flags) add username generator

generate username from full name and combine with random string.

shared/helper/generateRandomString.ts

@@ -0,0 +1,7 @@
+import { customAlphabet } from "nanoid";
+
+export const generateRandomString = (length: number = 10): string => {
+  const characters =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+  return customAlphabet(characters, length)();
+};