Optional query parameters with compile-time checks #645

It would be nice if we could specify optional query parameters such that we get compile failures if they aren't specified correctly.

Ideally, we could pass in in a POJO which can be used to generate the expected map through reflection.

Less ideally, allowing the query parameter map to have enum keys (no compile failure on invalid value types, but at least we will get a compile failure on an invalid parameter name).