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/storage_file.go

@@ -0,0 +1,48 @@
+package session
+
+import (
+	"context"
+	"os"
+	"sync"
+
+	"github.com/go-faster/errors"
+)
+
+// FileStorage implements SessionStorage for file system as file
+// stored in Path.
+type FileStorage struct {
+	Path string
+	mux  sync.Mutex
+}
+
+// LoadSession loads session from file.
+func (f *FileStorage) LoadSession(_ context.Context) ([]byte, error) {
+	if f == nil {
+		return nil, errors.New("nil session storage is invalid")
+	}
+
+	f.mux.Lock()
+	defer f.mux.Unlock()
+
+	data, err := os.ReadFile(f.Path)
+	if os.IsNotExist(err) {
+		return nil, ErrNotFound
+	}
+	if err != nil {
+		return nil, errors.Wrap(err, "read")
+	}
+
+	return data, nil
+}
+
+// StoreSession stores session to file.
+func (f *FileStorage) StoreSession(_ context.Context, data []byte) error {
+	if f == nil {
+		return errors.New("nil session storage is invalid")
+	}
+
+	f.mux.Lock()
+	defer f.mux.Unlock()
+	// TODO(tdakkota): use robustio/renameio?
+	return os.WriteFile(f.Path, data, 0600)
+}