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/tdesktop.go

@@ -0,0 +1,80 @@
+// Package tdesktop contains Telegram Desktop session decoder.
+package tdesktop
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"path"
+
+	"github.com/go-faster/errors"
+)
+
+// Account is a Telegram user account representation in Telegram Desktop storage.
+type Account struct {
+	// IDx is an internal Telegram Desktop account ID.
+	IDx uint32
+	// Authorization contains Telegram user and MTProto sessions.
+	Authorization MTPAuthorization
+	// Config contains Telegram config.
+	Config MTPConfig
+}
+
+// Read reads accounts info from given Telegram Desktop tdata root.
+// Shorthand for:
+//
+//	ReadFS(os.DirFS(root), passcode)
+func Read(root string, passcode []byte) ([]Account, error) {
+	return ReadFS(os.DirFS(root), passcode)
+}
+
+// ReadFS reads Telegram Desktop accounts info from given FS root.
+func ReadFS(root fs.FS, passcode []byte) ([]Account, error) {
+	keyDataFile, err := open(root, "key_data")
+	if err != nil {
+		return nil, errors.Wrap(err, "open key_data")
+	}
+
+	kd, err := readKeyData(keyDataFile, passcode)
+	if err != nil {
+		return nil, err
+	}
+	if len(kd.accountsIDx) < 1 {
+		return nil, ErrNoAccounts
+	}
+
+	r := make([]Account, 0, len(kd.accountsIDx))
+	for _, account := range kd.accountsIDx {
+		var keyFile = fileKey("data")
+		if account > 0 {
+			keyFile = fileKey(fmt.Sprintf("data#%d", account+1))
+		}
+
+		mtpDataFile, err := open(root, keyFile)
+		if err != nil {
+			return nil, errors.Wrap(err, "open key_data")
+		}
+
+		mtpData, err := readMTPData(mtpDataFile, kd.localKey)
+		if err != nil {
+			return nil, errors.Wrap(err, "read mtp")
+		}
+
+		a := Account{
+			IDx:           account,
+			Authorization: mtpData,
+		}
+		mtpConfigFile, err := open(root, path.Join(keyFile, "config"))
+		if err == nil {
+			mtpConfig, err := readMTPConfig(mtpConfigFile, kd.localKey)
+			// HACK: ignoring error, because config is optional.
+			if err == nil {
+				a.Config = mtpConfig
+			}
+		}
+
+		r = append(r, a)
+	}
+
+	return r, nil
+}