Initial webhook support

Core/WebhookAspNetProvider.cs

@@ -0,0 +1,40 @@
+#nullable enable
+
+using BotFramework.Abstractions.UpdateProvider;
+using BotFramework.Config;
+using Microsoft.Extensions.Options;
+using System.Threading;
+using System.Threading.Tasks;
+using Telegram.Bot;
+
+namespace Kruzya.TelegramBot.Core
+{
+    public class WebhookAspNetProvider : IWebhookProvider
+    {
+        private readonly ITelegramBotClient _client;
+        private readonly BotConfig _config;
+        private readonly string? _secretToken;
+
+        public WebhookAspNetProvider(ITelegramBotClient client, IOptions<BotConfig> config)
+        {
+            _client = client;
+            _config = config.Value;
+
+            _secretToken = _config.Webhook.SecretToken;
+            if (string.IsNullOrWhiteSpace(_secretToken))
+            {
+                _secretToken = null;
+            }
+        }
+
+        public async Task StartAsync(CancellationToken token)
+        {
+            await _client.SetWebhookAsync(_config.Webhook.Url, secretToken: _secretToken, cancellationToken: token);
+        }
+
+        public async Task StopAsync(CancellationToken token)
+        {
+            await _client.DeleteWebhookAsync(cancellationToken: token);
+        }
+    }
+}