anchor.diff:  <1> Install one of the available <<modules-template-engine, template engines>>
   <2> Install one of the available <<modules-json, json modules>>
   <3> Test if the accept header matches the `application/json` content type
  -<4> Render json or fallback to html 
  +<4> Render json if matches
  +<5> Render html as fallback
   
   === Catch by Code
   
  
positive.code:   error((ctx, cause, statusCode) -> {                                      <1>
      Router router = ctx.getRouter();
      router.getLog().error("found `{}` error", statusCode.value(), cause);  <2>
      ctx.setResponseStatusCode(statusCode);
      ctx.send("found `" + statusCode.value() + "` error");                  <3>
    });
  }
  
negative.code: == Error Handler
  
  Jooby catches application exception using the javadoc:ErrorHandler[] class. The
  javadoc:ErrorHandler[DEFAULT] error handler produces simple HTML page or JSON based on the value
  of the `ACCEPT` header and log the exception.
  
  