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/transport/obfuscated.go

@@ -0,0 +1,85 @@
+package transport
+
+import (
+	"bytes"
+	"io"
+	"net"
+
+	"github.com/go-faster/errors"
+	"go.uber.org/multierr"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/mtproxy/obfuscated2"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/proto/codec"
+)
+
+type obfListener struct {
+	listener net.Listener
+}
+
+type obfConn struct {
+	reader io.Reader
+	writer io.Writer
+	net.Conn
+}
+
+func (c *obfConn) Read(p []byte) (int, error) {
+	return c.reader.Read(p)
+}
+
+func (c *obfConn) Write(p []byte) (int, error) {
+	return c.writer.Write(p)
+}
+
+// ObfuscatedListener creates new obfuscated2 listener using given net.Listener.
+//
+// Useful for creating Telegram servers:
+//
+//	transport.Listen(transport.ObfuscatedListener(ln))
+func ObfuscatedListener(listener net.Listener) net.Listener {
+	return obfListener{listener: listener}
+}
+
+// Accept waits for and returns the next connection to the listener.
+func (l obfListener) Accept() (_ net.Conn, err error) {
+	conn, err := l.listener.Accept()
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		if err != nil {
+			multierr.AppendInto(&err, conn.Close())
+		}
+	}()
+
+	rw, md, err := obfuscated2.Accept(conn, nil)
+	if err != nil {
+		return nil, errors.Wrap(err, "accept")
+	}
+
+	var tag *bytes.Reader
+	if md.Protocol[0] == codec.AbridgedClientStart[0] {
+		// Abridged sends only byte for tag.
+		tag = bytes.NewReader(md.Protocol[:1])
+	} else {
+		tag = bytes.NewReader(md.Protocol[:])
+	}
+
+	accepted := &obfConn{
+		reader: io.MultiReader(tag, rw),
+		writer: rw,
+		Conn:   conn,
+	}
+
+	return accepted, nil
+}
+
+// Close closes the listener.
+// Any blocked Accept operations will be unblocked and return errors.
+func (l obfListener) Close() error {
+	return l.listener.Close()
+}
+
+// Addr returns the listener's network address.
+func (l obfListener) Addr() net.Addr {
+	return l.listener.Addr()
+}