title: adding the class id field to jsonschema for enums
body: <p>Is there a way to add the id property when generating jsonschema?
  Using the jackson databind, I am:</p>
  <pre><code>ObjectMapper mapper = new ObjectMapper();
  SchemaFactoryWrapper visitor = new SchemaFactoryWrapper();
  JsonSchemaGenerator jsg = new JsonSchemaGenerator(mapper, visitor);
  JsonSchema jsonSchema = jsg.generateSchema(Status.class);
  </code></pre>
  <p>On the following enum:</p>
  <pre><code>public enum Status {
      ON,
      OFF;
  }
  </code></pre>
  <p>It generates:</p>
  <pre><code>{
    &quot;type&quot; : &quot;string&quot;,
    &quot;enum&quot; : [ &quot;ON&quot;, &quot;OFF&quot; ]
  }
  </code></pre>
  <p>However, if would like it to include the id:</p>
  <pre><code>{
    &quot;id&quot;   : &quot;urn:jsonschema:com:example:enums:Status&quot;
    &quot;type&quot; : &quot;string&quot;,
    &quot;enum&quot; : [ &quot;ON&quot;, &quot;OFF&quot; ]
  }
  </code></pre>
  <p>Is this possible?</p>