reactor-core/src/main/java/reactor/core/publisher/Flux.java
public final <V> Mono<V> then(Mono<V> other) {
		return Mono.onAssembly(new MonoIgnoreThen<>(new Publisher[] { this }, other));
	}
public final <V> Mono<V> then(Mono<V> other) {
		return Mono.onAssembly(new MonoIgnoreThen<>(new Publisher[] { this }, other));
	}
Let this {@link Flux} complete then play signals from a provided {@link Mono}.
<p>
In other words ignore element from this {@link Flux} and transform its completion signal into the
emission and completion signal of a provided {@code Mono<V>}. Error signal is
replayed in the resulting {@code Mono<V>}.

<p>
<img class="marble" src="doc-files/marbles/thenWithMonoForFlux.svg" alt="">

@reactor.discard This operator discards elements from the source.

@param other a {@link Mono} to emit from after termination
@param <V> the element type of the supplied Mono

@return a new {@link Flux} that wait for source completion then emits from the supplied {@link Mono}