core/play/src/main/java/play/mvc/Call.java
public Call unique() {
    return new play.api.mvc.Call(method(), this.uniquify(this.url()), fragment());
  }
public Call unique() {
    return new play.api.mvc.Call(method(), this.uniquify(this.url()), fragment());
  }
Append a unique identifier to the URL.

@return a copy if this call with a unique identifier to this url