Optimised whole budget chart to use less queries.

app/Repositories/Budget/BudgetRepositoryInterface.php

@@ -32,6 +32,18 @@ interface BudgetRepositoryInterface
      */
     public function getExpensesPerDay(Budget $budget, Carbon $start, Carbon $end);
 
+    /**
+     * Returns the expenses for this budget grouped per month, with the date
+     * in "date" (a string, not a Carbon) and the amount in "dailyAmount".
+     *
+     * @param Budget $budget
+     * @param Carbon $start
+     * @param Carbon $end
+     *
+     * @return Collection
+     */
+    public function getExpensesPerMonth(Budget $budget, Carbon $start, Carbon $end);
+
     /**
      * @param Budget $budget
      *