title: Swagger does not validate enum query parameter
body: <p>I'm using swagger 2.0 to define my API. I'm using enums as described in the docs <a href="https://swagger.io/docs/specification/2-0/enums/" rel="noreferrer">here</a>. I have the following endpoint in my swagger.yml file:</p>
  
  <pre><code>/my-endpoint:
      x-swagger-router-controller: my-controller
      get:
        summary: my test endpoint
        parameters:
          - name: feeling
            in: query
            type: string
            enum:
              - happy
              - sad
            required: true
        produces:
          - application/json
        responses:
          200:
            description: OK
  </code></pre>
  
  <p>I would expect a <code>400 bad request</code> to be returned to the client if the <code>feeling</code> query parameter is not either <code>happy</code> or <code>sad</code>, but it accepts any string. Does swagger not validate that the parameter is in the enum?</p>