anchor.diff:  [source,java]
   ----
   @Route(path = "/mail")
  -Uni<Void> sendEmail(RoutingContext context) {
  +Uni<Void> sendEmail() {
       return mailer.send(...);
   }
   ----
   
   The item produced by the returned `Uni` can be:
   
  -* a string - written into the HTTP response directly
  -* a buffer - written into the HTTP response directly
  -* an object - written into the HTTP response after having been encoded into JSON.
  +* A string - written into the HTTP response directly.
  +* A `io.vertx.core.buffer.Buffer` - written into the HTTP response directly.
  +* An object - written into the HTTP response after having been encoded into JSON.
   The `content-type` header is set to `application/json` if not already set.
   
   If the returned `Uni` produces a failure (or is `null`), an HTTP 500 response is written.
  
positive.code: }
  ----
  <1> Header information about your API.
  <2> Defining the response
  
  This will generate this OpenAPI schema:
  
  
negative.code: [source, java]
  ----
  @Route(path = "/people", produces = ReactiveRoutes.APPLICATION_JSON)
  Multi<Person> people() {
      return Multi.createFrom().items(
              new Person("superman", 1),
              new Person("batman", 2),
  