chore: add an email validation before creating a user

Author: Victor

src/controllers/UserController.js

@@ -9,6 +9,12 @@ class UserController {
 
     async create(request, response) {
         const { name, email } = request.body;
+        const result = await User.find({ where: { email } });
+        const userFoundByEmail = result[0];
+
+        if (userFoundByEmail)
+            return response.status(400).json({ error: 'Email already exists!' });
+
         const user = await User.create({ name, email });
 
         return response.status(201).json(user);