title: AWS amplify authentication, enable only sign in - not sign up
body: <p>From all the great tutorials I looked for of how to add an auth module for a react app in amplify. The only type of module I see is a complete feature of sign in + sign up.</p>
  
  <p>What I'm trying to achieve is:</p>
  
  <ol>
  <li>Set up a custom Cognito user pool and add users to the pool manually. </li>
  <li>Add custom sign-in/login UI + code to a react amplify app.</li>
  <li>Disable anyone but me to add new users to the Cognito user pool manually.</li>
  </ol>
  
  <p>The website I'm working on is an internal website and I don't want anyone to be able to sign up via AppSync or the react client.</p>
  
  <p>Please help :)</p>