def report_filter_params
      Hash[*viable_report_filters.map{|filter| filter.filter_match_params}.flatten].
        merge(order: self.sorter)
    end
def report_filter_params
      Hash[*viable_report_filters.map{|filter| filter.filter_match_params}.flatten].
        merge(order: self.sorter)
    end
These are the built-in filter params that define this report. They are merged at a later
 step with the runtime params entered by the user for a specific report run.
 nb. the sorter column here may be overridden by a runtime sort if requested by the user.