feat: add promotion suggestions for Shop PO processing

Distribution/Features/Scheme/SchemeRepository.cs

@@ -49,6 +49,18 @@ public class SchemeRepository(AppDBContext context) : ISchemeRepository
     public async Task AddRedemptionAsync(Models.SchemeRedemption entity) =>
         await context.SchemeRedemptions.AddAsync(entity);
 
+    public async Task<List<Models.SchemeRedemption>> GetRedemptionsByShopPOAsync(Guid shopPOId)
+    {
+        var list = await context.SchemeRedemptions.Include(r => r.Scheme).Where(r => r.FK_ShopPOId == shopPOId).ToListAsync();
+        // Rows added earlier in this unit of work are not in the database yet; rows removed are still there.
+        foreach (var added in context.SchemeRedemptions.Local.Where(r => r.FK_ShopPOId == shopPOId && !list.Contains(r)))
+            list.Add(added);
+        return list.Where(r => context.Entry(r).State != EntityState.Deleted).ToList();
+    }
+
+    public void RemoveRedemption(Models.SchemeRedemption entity) =>
+        context.SchemeRedemptions.Remove(entity);
+
     public async Task<bool> HasRedemptionAsync(Guid schemeId, Guid shopPOId) =>
         await context.SchemeRedemptions.AnyAsync(r => r.FK_SchemeId == schemeId && r.FK_ShopPOId == shopPOId);