title: ObjectMapper : How to get the root element in snake case
body: <p>I am trying to read object and convert into string.  But the root element is getting changed from <code>payment_token</code> to <code>PaymentToken</code>. </p>
  
  <pre><code>ObjectMapper mapper = new ObjectMapper();
  mapper.setSerializationInclusion(Include.NON_NULL);
  mapper.configure(SerializationFeature.WRAP_ROOT_VALUE, true);
  mapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
  String requestString = mapper.writeValueAsString(paymentToken); //paymenttoken is valid object
  </code></pre>
  
  <p>Input Object:</p>
  
  <pre><code>{
      "payment_token": {
          "client_id": "test",
          "currency_code": "USD" 
      }
  }
  </code></pre>
  
  <p>Getting Output as:</p>
  
  <pre><code>{
      "PaymentToken": {
          "client_id": "test",
          "currency_code": "USD"
      }
  }
  </code></pre>
  
  <p>Help me to get the root object as it is in input ?</p>