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/mtproxy/faketls/record.go

@@ -0,0 +1,76 @@
+package faketls
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+
+	"github.com/go-faster/errors"
+)
+
+const maxTLSRecordDataLength = 16384 + 24
+
+type record struct {
+	Type    RecordType
+	Version [2]byte
+	Data    []byte
+}
+
+func readRecord(r io.Reader) (record, error) {
+	rec := record{}
+
+	buf := make([]byte, 5)
+	if _, err := io.ReadFull(r, buf); err != nil {
+		return record{}, err
+	}
+
+	rec.Type = RecordType(buf[0])
+	versionRaw := buf[1:3]
+	switch {
+	case bytes.Equal(versionRaw, Version13Bytes[:]):
+		rec.Version = Version13Bytes
+	case bytes.Equal(versionRaw, Version12Bytes[:]):
+		rec.Version = Version12Bytes
+	case bytes.Equal(versionRaw, Version11Bytes[:]):
+		rec.Version = Version11Bytes
+	case bytes.Equal(versionRaw, Version10Bytes[:]):
+		rec.Version = Version10Bytes
+	default:
+		return record{}, errors.Errorf("unknown protocol version %v", versionRaw)
+	}
+
+	length := binary.BigEndian.Uint16(buf[3:])
+	if length > maxTLSRecordDataLength {
+		return record{}, errors.New("record length is too big")
+	}
+
+	rec.Data = make([]byte, length)
+	if _, err := io.ReadFull(r, rec.Data); err != nil {
+		return record{}, err
+	}
+
+	return rec, nil
+}
+
+func writeRecord(w io.Writer, r record) (int, error) {
+	buf := [...]byte{
+		byte(r.Type),
+		r.Version[0], r.Version[1],
+	}
+
+	if _, err := w.Write(buf[:]); err != nil {
+		return 0, errors.Wrap(err, "type and version")
+	}
+
+	binary.BigEndian.PutUint16(buf[:2], uint16(len(r.Data)))
+	if _, err := w.Write(buf[:2]); err != nil {
+		return 0, errors.Wrap(err, "data length")
+	}
+
+	n, err := w.Write(r.Data)
+	if err != nil {
+		return 0, errors.Wrap(err, "data")
+	}
+
+	return n, nil
+}