title: Changing the undocumented "TypeError: Failed to fetch" response to a custom default response
body: <p>I have a question regarding the "Undocumented  TypeError: Failed to fetch" response inside the Swagger UI.</p>
  
  <p>This is not a CORS issue, I am not interested in fixing this error.
  Is there a way to present this response in some other way, can I create my own default placeholder response for this?
  This error would happen when the server is down. I want to have default response for this like: Server is down.</p>
  
  <p>I realize that there is a default option I can add to responses in yaml file, but this does not work if the server does not respond. Of course, there is no error code, there is just Status: (failed) (inside of the inspect Chrome network tab).</p>
  
  <p>Can I somehow cover this response, make it my own?</p>
  
  <p>If that is not possible, can I make any undocumented request default to some http response code, like 500 for example?</p>