[feat] Add Response caching

Octokit/Http/Connection.cs

@@ -7,6 +7,7 @@ using System.Net.Http;
 using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
+using Octokit.Caching;
 using Octokit.Internal;
 
 namespace Octokit
@@ -23,7 +24,7 @@ namespace Octokit
 
         readonly Authenticator _authenticator;
         readonly JsonHttpPipeline _jsonPipeline;
-        readonly IHttpClient _httpClient;
+        internal IHttpClient _httpClient;
 
         /// <summary>
         /// Creates a new connection instance used to make requests of the GitHub API.
@@ -650,6 +651,21 @@ namespace Octokit
             }
         }
 
+        /// <summary>
+        /// Sets response cache used by the connection.
+        /// </summary>
+        /// <remarks>
+        /// Setting this property will wrap existing <see cref="IHttpClient"/> in <see cref="CachingHttpClient"/>.
+        /// </remarks>
+        public IResponseCache ResponseCache
+        {
+            set
+            {
+                Ensure.ArgumentNotNull(value, nameof(value));
+                _httpClient = new CachingHttpClient(_httpClient, value);
+            }
+        }
+
         async Task<IApiResponse<string>> GetHtml(IRequest request)
         {
             request.Headers.Add("Accept", AcceptHeaders.StableVersionHtml);