title: swagger-codegen add annotation based on custom property description
body: <p>I am trying to do something like the following:</p>
  
  <p>In my schema JSON models section:</p>
  
  <pre><code>"MyObject": {
    "type": "object",
    "description": "my description",
    "properties": {
      "type": "string",
      "description": "my property description",
      "customAnnotation": "true"
    }
  }
  </code></pre>
  
  <p>So right out of the gate, I'm trying to extend JSON Schema - likely my first problem.  However, I do not know how to do this legitimately, if that is even possible.</p>
  
  <p>Snippet for use case for "customAnnotation" the moustache template (-l spring):</p>
  
  <pre><code>{{#vars}}
  {{^customAnnotation}}@CustomAnnotation {{/customAnnotation}}public {{{datatypeWithEnum}}} {{getter}}() {
      return {{name}};
  }
  {{/vars}}
  </code></pre>
  
  <p>Can I actually do something like this?  clues helpful (yes, I'm a newbie in this area)!</p>
  
  <p>Note:  I would also like to use the count of found "customAnnotation" > 0 to annotate a class.  Something like:</p>
  
  <pre><code>{{^containsCustomAnnotations}}@ContainsCustomAnnotations {{/hasCustomAnnotation}}public void MyClass {
  }
  </code></pre>
  
  <p>Thanks!</p>