title: ZuulFilter is not invoked
body: <p>I use: </p>
  
  <ul>
  <li>spring-boot 2.1.2.RELEASE </li>
  <li>spring-cloud Greenwich.RELEASE</li>
  </ul>
  
  <p>Zuul dependency:</p>
  
  <pre><code>implementation 'org.springframework.cloud:spring-cloud-starter-netflix-zuul'
  </code></pre>
  
  <p>I'm invoking a microservice from another one using zuul and load balanced rest template:</p>
  
  <pre><code>restTemplate.postForEntity("http://image/api/image", imageDto, ImageDto.class)
  </code></pre>
  
  <p>The request reaches the downstream service but the <code>Authorization</code> header (I tried with different ones) is not being set in the ZullFilter:</p>
  
  <pre><code>public class ZuulAuthFilter extends ZuulFilter {
  
      public static final String AUTHORIZATION_HEADER = "Authorization";
  
      public String filterType() {
          return PRE_TYPE;
      }
  
      public int filterOrder() {
          return PRE_DECORATION_FILTER_ORDER - 1;
      }
  
      public boolean shouldFilter() {
          return true;
      }
  
      public Object run() {
          RequestContext ctx = RequestContext.getCurrentContext();
          String authorizationValue = ctx.getRequest().getHeaders(AUTHORIZATION_HEADER).nextElement();
          ctx.addZuulRequestHeader(AUTHORIZATION_HEADER, authorizationValue);
          return null;
      }
  } 
  </code></pre>
  
  <p>I've also created a filter <code>@Bean</code>:</p>
  
  <pre><code>@Bean
  public ZuulAuthFilter zuulAuthFilter() {
      return new ZuulAuthFilter();
  }
  </code></pre>
  
  <p>Here is my zuul configuration:</p>
  
  <pre><code>zuul:
    sensitiveHeaders: Cookie,Set-Cookie
    ribbon:
      eager-load:
        enabled: true
  </code></pre>
  
  <p>It looks like the filter is not being invoked at all. I've added <code>System.exit(0)</code> to each overriden filter method and the app is still running.</p>
  
  <p>I've annotated the Application class with <code>@EnableZuulProxy</code></p>
  
  <p>What am I missing? Why the filter might not be invoked? Should it be invoked in my case at all?</p>