render json: %w( day week month ).map { | span |
    {"#{span}": policy_scope(Courier).where(status: 'Completed').send("group_by_#{span}", &:dateCompleted).map { |key, value| { date: key, volume: value.sum(&:volume).round, reward: value.sum(&:reward), collateral: value.sum(&:collateral)}}}}.as_json