code: public static Route problemHandling(final ThrowingConsumer<Exceptional, ? extends Exception> consumer,
              final Route fallback) {
  
          final Route route = call(Exceptional.class, consumer);
  
          return dispatch(contentType(),
                  on(PROBLEM).call(route),
                  on(X_DOT_PROBLEM).call(route),
                  on(X_DASH_PROBLEM).call(route),
                  anyContentType().call(fallback));
      }
docs: Produces a {@link Route route} that dispatches on the {@link Navigators#contentType() content type} and
  recognises {@code application/problem+json} as well as {@code application/x-problem+json} and
  {@code application/x.problem+json} as {@link Problem problems} and handles them given the supplied consumer.
  The given fallback will be used if none of the mentioned content types matches.
  
  @param consumer the exception handler
  @param fallback the fallback route
  @return a route for handling problems dynamically