public static async Task RemoveItemLocation(this PrimaryDbContext db, ItemLocation model)
        {
            var il = await db.ItemLocations.FindAsync(model.Id);

            db.ItemLocations.Remove(il);
            await db.SaveChangesAsync();
        }
        public static async Task UpdateItemLocation(this PrimaryDbContext db, Item i, Location l, int oldLocationId)
        {
            if (await i.Validate(l, db))
            {
                var il = await db.ItemLocations.FirstOrDefaultAsync(x => x.ItemId == i.Id && x.LocationId == oldLocationId);

                if (il != null)
                {
                    il.LocationId = l.Id;
                    await db.SaveChangesAsync();
                }
            }
        }
        public static async Task AddItemLocation(this PrimaryDbContext db, Item i, Location l)
        {
            if (await i.Validate(l, db))
            {
                var il = new ItemLocation
                {
                    ItemId     = i.Id,
                    LocationId = l.Id
                };

                await db.ItemLocations.AddAsync(il);

                await db.SaveChangesAsync();
            }
        }