Added subdomain for merchants

Author: armando-rodriguez-cko

README.md

@@ -73,6 +73,7 @@ ICheckoutApi api = CheckoutSdk.Builder().OAuth()
     .AuthorizationUri(new Uri("https://access.sandbox.checkout.com/connect/token")) // custom authorization URI, optional
     .Scopes(OAuthScope.Files, OAuthScope.Flow) // array of scopes, optional
     .Environment(Environment.Sandbox)
+    .EnvironmentSubdomain("subdomain") // optional, Merchant-specific DNS name
     .LogProvider(logFactory) // optional
     .HttpClientFactory(httpClientFactory) // optional
     .Build();
@@ -89,6 +90,7 @@ Checkout.Previous.ICheckoutApi api = CheckoutSdk.Builder()
     .PublicKey("public_key") // optional, only required for operations related with tokens
     .SecretKey("secret_key")
     .Environment(Environment.Sandbox)
+    .EnvironmentSubdomain("subdomain") // optional, Merchant-specific DNS name
     .LogProvider(logFactory) // optional
     .HttpClientFactory(httpClientFactory) // optional
     .Build();

src/CheckoutSdk/AbstractCheckoutSdkBuilder.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Text.RegularExpressions;
 #if (NETSTANDARD2_0_OR_GREATER || NETCOREAPP3_1_OR_GREATER)
 using Microsoft.Extensions.Logging;
 #endif
@@ -7,6 +9,7 @@ namespace Checkout
     public abstract class AbstractCheckoutSdkBuilder<T>
     {
         protected Environment Env = Checkout.Environment.Sandbox;
+        private EnvironmentSubdomain _envSubdomain;
         protected IHttpClientFactory ClientFactory = new DefaultHttpClientFactory();
 
         public AbstractCheckoutSdkBuilder<T> Environment(Environment environment)
@@ -15,6 +18,12 @@ public AbstractCheckoutSdkBuilder<T> Environment(Environment environment)
             return this;
         }
 
+        public AbstractCheckoutSdkBuilder<T> EnvironmentSubdomain(string subdomain)
+        {
+            _envSubdomain = new EnvironmentSubdomain(Env, subdomain);
+            return this;
+        }
+
 #if (NETSTANDARD2_0_OR_GREATER || NETCOREAPP3_1_OR_GREATER)
         public AbstractCheckoutSdkBuilder<T> LogProvider(ILoggerFactory loggerFactory)
         {
@@ -31,7 +40,7 @@ public AbstractCheckoutSdkBuilder<T> HttpClientFactory(IHttpClientFactory httpCl
 
         protected CheckoutConfiguration GetCheckoutConfiguration()
         {
-            return new CheckoutConfiguration(GetSdkCredentials(), Env, ClientFactory);
+            return new CheckoutConfiguration(GetSdkCredentials(), Env, _envSubdomain, ClientFactory);
         }
 
         protected abstract SdkCredentials GetSdkCredentials();