Add custom HttpClient support to BotConfiguration

Introduce a new property `HttpClient` in the `BotConfiguration` class, allowing for a custom `HttpClient` to be set. If not set, a default `HttpClient` will be used.

Update `BotBuilder` to use this custom `HttpClient` when creating an instance of `TelegramBotClient`. If the `HttpClient` is not provided in the `BotConfiguration`, the default behavior remains unchanged.

Include a `using` directive for `System.Net.Http` in `BotConfiguration` to support the new `HttpClient` property.

Author: bvdcode

Sources/TelegramBot/Builders/BotBuilder.cs

@@ -144,7 +144,7 @@ public IBot Build()
                 throw new ArgumentNullException("TelegramBotToken", "The Telegram bot token is not set.");
             }
             TelegramBotClientOptions options = new TelegramBotClientOptions(_token, _baseApiUrl);
-            TelegramBotClient client = new TelegramBotClient(options);
+            TelegramBotClient client = new TelegramBotClient(options, httpClient: _botConfiguration.HttpClient);
             Services.AddSingleton<ITelegramBotClient>(client);
             bool hasKeyValueProvider = Services.Any(service => service.ServiceType == typeof(IKeyValueProvider));
             if (!hasKeyValueProvider)

Sources/TelegramBot/Builders/BotConfiguration.cs

@@ -1,4 +1,6 @@
-namespace TelegramBot.Builders
+using System.Net.Http;
+
+namespace TelegramBot.Builders
 {
     /// <summary>
     /// Bot configuration.
@@ -9,5 +11,10 @@ public class BotConfiguration
         /// Gets or sets a value indicating whether the bot should receive updates. Default is <see langword="true"/>.
         /// </summary>
         public bool ReceiveUpdates { get; set; } = true;
+
+        /// <summary>
+        /// Gets or sets a value for custom HTTP client. If not set, a default <see cref="HttpClient"/> will be used.
+        /// </summary>
+        public HttpClient? HttpClient { get; set; } = null;
     }
 }