code: public final Mono<Boolean> hasElement(T value) {
  		Objects.requireNonNull(value, "value");
  		return any(t -> Objects.equals(value, t));
  	}
docs: Emit a single boolean true if any of the elements of this {@link Flux} sequence is
  equal to the provided value.
  <p>
  The implementation uses short-circuit logic and completes with true if
  an element matches the value.
  
  <p>
  <img class="marble" src="doc-files/marbles/hasElementForFlux.svg" alt="">
  
  @param value constant compared to incoming signals
  
  @return a new {@link Flux} with <code>true</code> if any element is equal to a given value and <code>false</code>
  otherwise