Hi, our old custom ORM supported pojos with Maps with non-string keys, IF it was a ObjectId or if it was an enum (because both are rather easily converted to and from string).

The standard ORM model does not allow this and requires the key to be a String (MapPropertyCodecProvider).

Which is fine, but it throws an exception if the key is not a String. This prevents me from making a custom PropertyCodecProvider. Since the MapPropertyCodecProvider is higher up the chain...

I think MapPropertyCodecProvider should not throw an exception if the map key is not a string, and just pass it on to other PropertyCodecProvider.