Refactor AmazonShipping options and formatting

- Adjusted spacing in the AddAmazonShippingClient method for consistency.
- Removed 'required' keyword from ClientId, ClientSecret, and RefreshToken properties in AmazonShippingApiOptions, making them optional.
- Assigned default values of string.Empty to ClientId, ClientSecret, and RefreshToken.

src/EasyKeys.Shipping.Amazon.Abstractions/DependencyInjection/AmazonShippingServiceCollectionExtensions.cs

@@ -12,7 +12,7 @@ public static IServiceCollection AddAmazonShippingClient(
         string sectionName = nameof(AmazonShippingApiOptions),
         Action<AmazonShippingApiOptions, IServiceProvider>? configure = null)
     {
-        //services.AddChangeTokenOptions<AmazonShippingApiOptions>(sectionName, null, (options, config) => configure?.Invoke(options, config));
+        services.AddChangeTokenOptions<AmazonShippingApiOptions>(sectionName, null, (options, config) => configure?.Invoke(options,config));
         services.AddSingleton<IAmazonApiAuthenticatorService, AmazonApiAuthenticatorService>();
         // add generated api clients
         // services.AddHttpClient<AuthorizationApi>();

src/EasyKeys.Shipping.Amazon.Abstractions/Options/AmazonShippingApiOptions.cs

@@ -1,15 +1,10 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+namespace EasyKeys.Shipping.Amazon.Abstractions.Options;
 
-namespace EasyKeys.Shipping.Amazon.Abstractions.Options;
 public class AmazonShippingApiOptions
 {
-    required public string ClientId { get; set; }
+    public string ClientId { get; set; } = string.Empty;
 
-    required public string ClientSecret { get; set; }
-    
-    required public string RefreshToken { get; set; } 
+    public string ClientSecret { get; set; } = string.Empty;
+
+    public string RefreshToken { get; set; } = string.Empty;
 }