title: How to secure ClientID in OAuth2?
body: <p>We want to develop an Angular 2 App with an external OAuth2 server (IdentityServer4).</p>
  
  <p>We also want to identify each client for uniqueness. But how to protect the ClientID in the Angular 2 / Javascript source?
  Do we have to work here with CORS and check for the origin of the request? Do we have to build a server-side application for the authentication?</p>
  
  <p>Our Mobile App should use the ClientID 12345
  Our Angular App should use ClientID 99999</p>
  
  <p>But if anybody else would try to use ClientID 12345 it should be rejected.</p>
  
  <p>What is the best practise here?
  - Authenticate directly with Angular?
  - Use for each angular App a Serverapp for Auth?</p>