code: @SafeVarargs
    public final <G, ERR> OrFuture<G, Every<ERR>>
    when(OrFuture<? extends G, ? extends Every<? extends ERR>> or,
         Function<? super G, ? extends Validation<ERR>>... validations) {
  
      OrPromise<G, Every<ERR>> promise = promise();
      or.onComplete(o -> promise.complete(Accumulation.when(o, validations)));
      return promise.future();
    }
docs: Enables further validation on an existing accumulating OrFuture by passing validation functions.
  
  @param <G>         the Good type of the argument OrFuture
  @param <ERR>       the type of the error message contained in the accumulating failure
  @param or          the accumulating OrFuture
  @param validations the validation functions
  @return the original or if it passed all validations or a Bad with all failures