JSONAPIURLBuilder::buildPageParam() (and likely others) have undefined properties serialized as undefined in query param

[bradjones1]

I wanted to use .page({limit: 10}) in a findRecords transform, however if you don't also provide the offset key, its value gets serialized into undefined (the literal string) in the query param, making my backend choke. I couldn't quite figure out where the serialization happens, but I figure this method (and likely others) need to handle absent optional parameters by excluding them?