This MR adds the ability to define parameters of type `List<T>`. I don't know if this feature was planned but I think it would be a nice addition. The current implementation adds two new methods in `Parameters` to define named and unnamed list parameters: ```kotlin // Named list parameter var tags by listParameter<String>("search_tags") // Unnamed list parameter var tags by listParameter<String>() ``` List parameters cannot set a custom default value: their default value is always `emptyList()`. Naturally, parameters with an empty list as value are not emitted to the server. The implementation on the client and server side didn't require much extra work as Ktor natively supports query parameters with multiple values. I'm open for feedback on the implementation and the naming of the methods. See merge request opensavvy/groundwork/spine!94