move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/session/tdesktop_example_test.go

@@ -0,0 +1,73 @@
+package session_test
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/session"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/session/tdesktop"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/telegram"
+)
+
+func ExampleTDesktopSession() {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		panic(err)
+	}
+
+	root := filepath.Join(home, "Downloads", "Telegram", "tdata")
+	accounts, err := tdesktop.Read(root, nil)
+	if err != nil {
+		panic(err)
+	}
+
+	data, err := session.TDesktopSession(accounts[0])
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(data.DC, data.Addr)
+}
+
+func ExampleTDesktopSession_convert() {
+	ctx := context.Background()
+
+	home, err := os.UserHomeDir()
+	if err != nil {
+		panic(err)
+	}
+
+	root := filepath.Join(home, "Downloads", "Telegram", "tdata")
+	accounts, err := tdesktop.Read(root, nil)
+	if err != nil {
+		panic(err)
+	}
+
+	data, err := session.TDesktopSession(accounts[0])
+	if err != nil {
+		panic(err)
+	}
+
+	var (
+		storage = new(session.StorageMemory)
+		loader  = session.Loader{Storage: storage}
+	)
+
+	// Save decoded Telegram Desktop session as gotd session.
+	if err := loader.Save(ctx, data); err != nil {
+		panic(err)
+	}
+
+	// Create client.
+	client := telegram.NewClient(telegram.TestAppID, telegram.TestAppHash, telegram.Options{
+		SessionStorage: storage,
+	})
+	if err := client.Run(ctx, func(ctx context.Context) error {
+		// Use Telegram Desktop session.
+		return nil
+	}); err != nil {
+		panic(err)
+	}
+}