Consider using Serializer<?> for the delegates of DelegatingByTypeSerializer

[v-chernyshev]

Expected Behavior

I've tried using the newly added assignable types support and, initially, wrote the following code:

final var delegates = new LinkedHashMap<Class<?>, Serializer<?>>();
delegates.put(Message.class, new ProtobufMessageSerializer());
delegates.put(byte[].class, new ByteArraySerializer());

return new DefaultKafkaProducerFactory<>(
        this.springProperties.buildProducerProperties(),
        new VoidSerializer(),
        new DelegatingByTypeSerializer(delegates, true));

Where ProtobufMessageSerializer is a custom type that can handle any protobuf message. Unfortunately, the code does not compile because the constructor of DelegatingByTypeSerializer and the internal member variables all expect to see the raw Serializer type. It is, of course, possible to tweak the code to:

final var delegates = new LinkedHashMap<Class<?>, Serializer>();

But then a warning is raised to highlight the usage of raw types. Generally we treat this warning type as an error.

Current Behavior

I am basically forced to do this instead to silence the warning:

@SuppressWarnings("rawtypes")
final var delegates = new LinkedHashMap<Class<?>, Serializer>();

Context

Our project uses the retryable topics feature, @SendTo and the ErrorHandlingDeserializer class to intercept potential poison pill messages. They are, however, extremely unlikely to happen, so I'd like to make sure that the first delegate that's checked at runtime is the base protobuf Message class. As far as I know, the only way to guarantee the iteration order is to explicitly populate a LinkedHashMap, but creating such a map requires warning suppression.