Fix and simplify bill repos

app/Repositories/Bill/BillRepositoryInterface.php

@@ -131,6 +131,17 @@ interface BillRepositoryInterface
      */
     public function getOverallAverage($bill): string;
 
+    /**
+     * Between start and end, tells you on which date(s) the bill is expected to hit.
+     *
+     * @param Bill   $bill
+     * @param Carbon $start
+     * @param Carbon $end
+     *
+     * @return Collection
+     */
+    public function getPayDatesInRange(Bill $bill, Carbon $start, Carbon $end): Collection;
+
     /**
      * @param Bill $bill
      *