title: JsonAnyGetter / JsonAnySetter the resulting JSON has doubled values
body: <p>I need to write a JSON string that follows this basic format:</p>
  
  <pre><code>"gesamtAngebot":{
      "angebotList":[{
          "instanzId":"string",
          "buchungsKontextList":[{
              "quellSystem":"SOMETHING",
              "payload":{}
          }],
          "payload":{"test1":"test1"}
      }]
  }
  </code></pre>
  
  <p>I'm using the following class to present the data, and an instance of this class is serialized with the Jackson ObjectMapper.</p>
  
  <pre><code>@Data
  public class Angebot {
  
      private String instanzId;
  
      private List&lt;BuchungsKontext&gt; buchungsKontextList;
  
      private Map&lt;String, Object&gt; payload = new HashMap&lt;String, Object&gt;();
  
      @JsonAnyGetter
      public Map&lt;String, Object&gt; any() {
          return payload;
      }
  
      @JsonAnySetter
      public void set(String name, Object value) {
          payload.put(name, value);
      }
  }
  </code></pre>
  
  <p>If I serialize an instance of this class as-is, the resulting JSON will be something like this:</p>
  
  <pre><code>"gesamtAngebot":{
      "angebotList":[{
          "instanzId":"string",
          "buchungsKontextList":[{
              "quellSystem":"SOMETHING",
              "payload":{}
          }],
          "payload":{"test1":"test1"},
          "test1":"test1"
      }]
  }
  </code></pre>
  
  <p>As you can see the data of "payload" is doubled as it's own element and I don't have any idea why.</p>
  
  <p>Thanks in advance for your attention and advice.</p>