Fixed all relationship and write errors in all entities

PyroFetes/Models/WarehouseProduct.cs

@@ -1,14 +1,15 @@
 using System.ComponentModel.DataAnnotations;
+using Microsoft.EntityFrameworkCore;
 
 namespace PyroFetes.Models;
 
+[PrimaryKey(nameof(ProductId), nameof(WarehouseId))]
 public class WarehouseProduct
 {
-    [Key] public int Quantity { get; set; }
-    
     [Required] public int ProductId { get; set; }
-    [Required] public Product? Product { get; set; }
-    
+    public Product? Product { get; set; }
     [Required] public int WarehouseId { get; set; }
-    [Required] public Warehouse? Warehouse { get; set; }
+    public Warehouse? Warehouse { get; set; }
+    
+    [Required] public int Quantity { get; set; }
 }