AggregateReference bug

Referring to the usage method of the document:

  @GetMapping(path = "/scanners")
  ResponseEntity<?> getProducers(
    @RequestParam AggregateReference<Producer, ProducerIdentifier> producer) {

    var identifier = producer.resolveRequiredId();
    // Alternatively
    var aggregate = producer.resolveRequiredAggregate();
  }

The following information is returned:

Source to convert from must be an instance of [java.lang.String]; instead it was a [java.net.URI]

Start with the documented AggregateReference usage shown in the issue and reproduce the @RequestParam endpoint with the URI value. Trace the conversion that produces the String-versus-URI error; done means the producer reference resolves successfully through the documented method.