Add item tracking migrations

Distribution/Models/ItemBatch.cs

@@ -0,0 +1,20 @@
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Distribution.Models
+{
+    /// <summary>
+    /// Backs both batch/lot tracking and expiry-only tracking for an item. BatchNumber is null
+    /// when the item tracks an expiry date but not a batch number (TracksExpiryDate without
+    /// TracksBatches).
+    /// </summary>
+    public class ItemBatch : Template
+    {
+        public Guid FK_ItemId { get; set; }
+        [ForeignKey("FK_ItemId")]
+        public Item Item { get; set; }
+
+        public string? BatchNumber { get; set; }
+        public DateTime? ManufactureDate { get; set; }
+        public DateTime? ExpiryDate { get; set; }
+    }
+}