Added event handlers in Fieldbehaviour to react to watering can state changes

scripts/CSharp/Common/Farming/FieldBehaviour2D.cs

@@ -79,9 +79,17 @@ public partial class FieldBehaviour2D : Sprite2D, ISaveable
 
     public override void _EnterTree()
     {
+        WateringCanState.OnFill += UpdateInteractionArea;
+        WateringCanState.OnEmpty += UpdateInteractionArea;
         LoadFromSaveData();
     }
 
+    public override void _ExitTree()
+    {
+        WateringCanState.OnFill -= UpdateInteractionArea;
+        WateringCanState.OnEmpty -= UpdateInteractionArea;
+    }
+
     public override void _Ready()
     {
         if(PlantingPlaceholder.GetChildCount() > 0)

scripts/CSharp/Common/Farming/WateringCanState.cs

@@ -30,6 +30,7 @@ public static class WateringCanState
     public static event WateringCanDelegate WateringCanActiveStateChanged;
     public static event Action? OnWater;
     public static event Action? OnFill;
+    public static event Action? OnEmpty;
         
 
     
@@ -52,6 +53,11 @@ public static class WateringCanState
             _fillstate--;
             OnWater?.Invoke();
         }
+
+        if (_fillstate == 0)
+        {
+            OnEmpty?.Invoke();
+        }
     }
 
     /// <summary>