title: Feign client custom interceptor for JWT token validation
body: <p>I am new to spring and feign and exploring since a couple of days.
  I am able to make auth request to our protected resources(username/password) and using the JWT token returned by auth service in the subsequent request headers.
  However, i would like to call the auth service only when the token is expired using the same credentials.Spring cloud has OAuth2FeignRequestInterceptor which is doing exactly the same thing but using client id and secret key.</p>
  
  <p>Any such custom interceptors for handling tokens generated by username and password?</p>