add methods to incement and decrement total spots

code/CarSpotController.cpp

@@ -29,6 +29,14 @@ class CarSpotController {
             this->occupied_spots++;
         }
 
+        void increment_total_spots () {
+            this->total_spots++;
+        }
+
+        void decrement_total_spots () {
+            this->total_spots--;
+        }
+
         void decrement_occupied_spots () {
             this->occupied_spots--;
         }