added missing endpoint

packages/server/src/controllers/UserController/endpoints/checkEmailAvailable.js

@@ -0,0 +1,15 @@
+import { User } from "@models"
+
+export default {
+    method: "GET",
+    route: "/email_available",
+    fn: async (req, res) => {
+        const user = await User.findOne({
+            email: req.query.email,
+        })
+
+        return res.json({
+            available: !user,
+        })
+    }
+}