anchor.diff:  wrap and rethrow) could be achieved:
   [source,java]
   ----
  -Flux.just("key1")
  +Flux.just("timeout1")
       .flatMap(k -> callExternalService(k)
           .onErrorResumeWith(original -> Flux.error(
  -            new BusinessException("oops", original))
  +            new BusinessException("oops, SLA exceeded", original))
           )
       );
   ----
  
positive.code: ----
  Flux.just(10)
      .map(this::doSomethingDangerous)
      .onErrorReturn("DEFAULT_VALUE");
  ----
  
  You also have the option of dynamically choosing the single value depending on
  the exception that occurred:
  [source,java]
  ----
  Flux.just(10)
      .map(this::doSomethingDangerous)
      .onErrorReturn(e -> valueForError(e));
  ----
  
  If you want more than a single default value and you have an alternative safer
  
negative.code: It takes a `Function` that maps the error to the fallback sequence to switch to:
  [source,java]
  ----
  Flux.just("timeout1", "unknown", "key2")
      .flatMap(k ->
          callExternalService(k)
            .onErrorResumeWith(error -> { <1>
  