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/obfuscator/obfuscator.go

@@ -0,0 +1,52 @@
+// Package obfuscator contains some MTProxy obfuscation utilities.
+package obfuscator
+
+import (
+	"io"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/mtproxy"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/mtproxy/faketls"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/mtproxy/obfuscated2"
+)
+
+// Obfuscator represents MTProxy obfuscator.
+type Obfuscator interface {
+	io.ReadWriter
+	Handshake(protocol [4]byte, dc int, s mtproxy.Secret) error
+}
+
+type tls struct {
+	ftls  *faketls.FakeTLS
+	obfs2 *obfuscated2.Obfuscated2
+}
+
+func newTLS(rand io.Reader, conn io.ReadWriter) tls {
+	ftls := faketls.NewFakeTLS(rand, conn)
+	obfs2 := obfuscated2.NewObfuscated2(rand, ftls)
+	return tls{
+		ftls:  ftls,
+		obfs2: obfs2,
+	}
+}
+
+func (t tls) Write(p []byte) (int, error) {
+	return t.obfs2.Write(p)
+}
+
+func (t tls) Read(p []byte) (int, error) {
+	return t.obfs2.Read(p)
+}
+
+func (t tls) Handshake(protocol [4]byte, dc int, s mtproxy.Secret) error {
+	if err := t.ftls.Handshake(protocol, dc, s); err != nil {
+		return errors.Wrap(err, "faketls handshake")
+	}
+
+	if err := t.obfs2.Handshake(protocol, dc, s); err != nil {
+		return errors.Wrap(err, "obfs2 handshake")
+	}
+
+	return nil
+}