Macro impl_pagination_params 

macro_rules! impl_pagination_params {
    ($param_type:ty, {
        limit: $limit_field:ident,
        after: $after_field:ident,
        $(before: $before_field:ident,)?
        $(order: $order_field:ident,)?
        $(filter: $filter_field:ident,)?
    }) => { ... };
}

Generic macro to implement PaginationParams