Refactor namespaces to follow new naming convention and add item model classes

Models/Inventory.cs

@@ -0,0 +1,28 @@
+namespace Pet.Companion.Models
+{
+    public class Inventory
+    {
+        public List<Item> Items { get; set; } = new();
+        public int Capacity { get; set; }
+
+        public bool AddItem(Item item)
+        {
+            if (Items.Count < Capacity)
+            {
+                Items.Add(item);
+                return true;
+            }
+            return false;
+        }
+
+        public bool RemoveItem(Item item)
+        {
+            return Items.Remove(item);
+        }
+
+        public void TrashItem(Item item)
+        {
+            RemoveItem(item);
+        }
+    }
+}