title: How add header for swagger generation based on annotation?
body: <p>Consider example:</p>
  
  <pre><code>@RequestMapping("myPath")
  public Mono&lt;MyDto&gt; myMethod(@RequestParam(value = "amount") Long amount, @AuthenticationPrincipal MyUser user) {
  
  } 
  </code></pre>
  
  <p>To skip <code>MyUser</code> from parameter list I have added <code>@AuthenticationPrincipal</code> to exclusions and springfox generated swagger docs like that:</p>
  
  <pre><code>"/myPath": {
    "get": {
      "tags": [
        "my-controller"
      ],
      "summary": "myMethod",
      "operationId": "myMethodUsingGET",
      "produces": [
        "*/*"
      ],
      "parameters": [
        {
          "name": "amount",
          "in": "query",
          "description": "amount",
          "required": true,
          "type": "integer",
          "format": "int64"
        }
      ],
      "responses": {
        "200": {
          "description": "OK",
          "schema": {
            "$ref": "#/definitions/Mono«MyDto»"
          }
        },
        "401": {
          "description": "Unauthorized"
        },
        "403": {
          "description": "Forbidden"
        },
        "404": {
          "description": "Not Found"
        }
      },
      "deprecated": false
    }
  }
  </code></pre>
  
  <p>Here is spring configuration:</p>
  
  <pre><code>@Configuration
  @EnableSwagger2WebFlux
  public class SwaggerConfig {
      @Bean
      public Docket api() {
          Class[] clazz = {AuthenticationPrincipal.class};
  
          return new Docket(DocumentationType.SWAGGER_2)
                  .select()
                  .paths(PathSelectors.any())
                  .build()
                  .ignoredParameterTypes(clazz);
      }
  }
  </code></pre>
  
  <p>Is there a way to add a header into swagger documentation generated by <a href="http://springfox.github.io/springfox/" rel="nofollow noreferrer">springfox</a> project for every path where <code>@AuthenticationPrincipal</code> specified?
  E.g. ignore <code>MyUser</code> class as parameter (or parameter group) and replace it with header (like <code>My-Auth-Header</code>) for all <code>@RequestMapping</code> method where <code>@AuthenticationPrincipal</code> is found.</p>