docs: public static <T> Publisher<T> createEmptyPublisher( Supplier<CompletionStage<Void>> supplier )
      {
          return Mono.create( sink -> supplier.get().whenComplete( ( ignore, completionError ) -> {
              Throwable error = Futures.completionExceptionCause( completionError );
              if ( error != null )
              {
                  sink.error( error );
              }
              else
              {
                  sink.success();
              }
          } ) );
      }