Use correct KType when custom InputValue is provided

[ESchouten]

When a custom InputTypeDef is provided, the kqlInput is correctly set, but the inputType is not.

Due to kotlins reflection behaviour, which returns functions with generic types instead of the underlying types, overriding the input type seems mandatory. https://youtrack.jetbrains.com/issue/KT-42746 Doing so enables the use of generics discussed in #139

Example:

inline fun <reified T : Any, reified U : Any, V: UseCase<T, U>> SchemaBuilder.connection(usecase: V) {
    query(usecase::class.simpleName!!) {
        resolver { request: T, ctx: Context ->
            usecase.execute(request, ctx.get<User>())
        }.returns<U>().apply {
            addInputValues(listOf(InputValueDef(T::class, "request")))
        }
    }
}