Fix Discord Webhooks logging sink not working

Seems like a recent update broke them. Before we were not closing the SSL
stream (we were just closing the tcp socket outright), now we read the
remaining data, close the SSL stream and finally the socket.

src/Multirole/Service/LogHandler/DiscordWebhookSink.cpp

@@ -45,6 +45,7 @@ class DiscordWebhookSink::Connection final : public std::enable_shared_from_this
 	boost::asio::ssl::stream<boost::asio::ip::tcp::socket> socket;
 	const Endpoints& endpoints;
 	const std::string payload;
+	std::string read_buffer;
 
 	void DoHandshake() noexcept
 	{
@@ -62,7 +63,32 @@ class DiscordWebhookSink::Connection final : public std::enable_shared_from_this
 	{
 		auto self(shared_from_this());
 		boost::asio::async_write(socket, boost::asio::buffer(payload),
-		[self](boost::system::error_code /*unused*/, std::size_t /*unused*/){});
+		[this, self](boost::system::error_code ec, std::size_t /*unused*/)
+		{
+			if(ec)
+				return;
+			DoRead();
+		});
+	}
+
+	void DoRead() noexcept
+	{
+		auto self(shared_from_this());
+		boost::asio::async_read_until(socket, boost::asio::dynamic_buffer(read_buffer), "\r\n\r\n",
+		[this, self](boost::system::error_code ec, std::size_t /*unused*/)
+		{
+			if(ec)
+				return;
+			DoShutdown();
+		});
+	}
+
+	void DoShutdown() noexcept
+	{
+		auto self(shared_from_this());
+		socket.async_shutdown([this, self](boost::system::error_code ec){
+			socket.lowest_layer().shutdown(boost::asio::ip::tcp::socket::shutdown_both, ec);
+		});
 	}
 };