Refactor to introduce nullable types and reduce compiler warnings (#801)

* Introduce nullable types to Core, Infrastructure and PublicApi projects

* Refactor unit tests

* Fixed failing tests

* Introduce Parameter object for CatalogItem update method

* Refactor CataloItemDetails param object

* Refactor following PR comments

src/Infrastructure/Data/CatalogContext.cs

@@ -8,9 +8,8 @@ namespace Microsoft.eShopWeb.Infrastructure.Data;
 
 public class CatalogContext : DbContext
 {
-    public CatalogContext(DbContextOptions<CatalogContext> options) : base(options)
-    {
-    }
+    #pragma warning disable CS8618 // Required by Entity Framework
+    public CatalogContext(DbContextOptions<CatalogContext> options) : base(options) {}
 
     public DbSet<Basket> Baskets { get; set; }
     public DbSet<CatalogItem> CatalogItems { get; set; }

src/Infrastructure/Data/Config/BasketConfiguration.cs

@@ -9,7 +9,7 @@ public class BasketConfiguration : IEntityTypeConfiguration<Basket>
     public void Configure(EntityTypeBuilder<Basket> builder)
     {
         var navigation = builder.Metadata.FindNavigation(nameof(Basket.Items));
-        navigation.SetPropertyAccessMode(PropertyAccessMode.Field);
+        navigation?.SetPropertyAccessMode(PropertyAccessMode.Field);
 
         builder.Property(b => b.BuyerId)
             .IsRequired()

src/Infrastructure/Data/Config/OrderConfiguration.cs

@@ -10,7 +10,7 @@ public class OrderConfiguration : IEntityTypeConfiguration<Order>
     {
         var navigation = builder.Metadata.FindNavigation(nameof(Order.OrderItems));
 
-        navigation.SetPropertyAccessMode(PropertyAccessMode.Field);
+        navigation?.SetPropertyAccessMode(PropertyAccessMode.Field);
 
         builder.Property(b => b.BuyerId)
             .IsRequired()

src/Infrastructure/Data/FileItem.cs

@@ -2,10 +2,10 @@
 
 public class FileItem
 {
-    public string FileName { get; set; }
-    public string Url { get; set; }
+    public string? FileName { get; set; }
+    public string? Url { get; set; }
     public long Size { get; set; }
-    public string Ext { get; set; }
-    public string Type { get; set; }
-    public string DataBase64 { get; set; }
+    public string? Ext { get; set; }
+    public string? Type { get; set; }
+    public string? DataBase64 { get; set; }
 }

src/Infrastructure/Infrastructure.csproj

@@ -3,6 +3,7 @@
 	<PropertyGroup>
 		<TargetFramework>net6.0</TargetFramework>
 		<RootNamespace>Microsoft.eShopWeb.Infrastructure</RootNamespace>
+		<Nullable>enable</Nullable>
 	</PropertyGroup>
 
 	<ItemGroup>