title: Dynamically add CORS Mappings to Rest Controller at runtime
body: <p>
  Hi! I am a beginner in Spring Boot. I have a simple Java Spring Boot Application which uses a Rest Controller. Some of the controller's endpoints are exposed to CORS requests. I've found out that it is possible to allow CORS requests by adding @CrossOrigin(origins ="..") annotations above the methods. 
  
  My problem is that I don't know all the origins at the moment and will have to add some of them later during the runtime of my Spring Boot Application.
  
  Is it possible to have a method to manually add new origin-addresses to some endpoints of my Rest Controller? E.g. to have an endpoint in my Rest Controller that allows a particular user (e.g.Admin) to add new cors-origins to a rest endpoint? If yes: Please give a simple example.
  </p>