Lots of additions and restructuring

TOOHUCardAPI/Data/Repositories/CardRepository.cs

@@ -0,0 +1,27 @@
+using System.Threading.Tasks;
+using Microsoft.EntityFrameworkCore;
+using TOOHUCardAPI.Data.Models;
+
+namespace TOOHUCardAPI.Data.Repositories
+{
+    public class CardRepository
+    {
+        private readonly AppDbContext _context;
+
+        public CardRepository(AppDbContext context)
+        {
+            _context = context;
+        }
+
+        public async Task<Card> GetCardByItemCode(string itemCode, bool allowNull = false)
+        {
+            Card card = await _context.Cards.FirstOrDefaultAsync(card => card.ItemCode == itemCode);
+            if (card == null && !allowNull)
+            {
+                throw new InvalidCardException();
+            }
+
+            return card;
+        }
+    }
+}