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/proto/unencrypted_message_test.go

@@ -0,0 +1,26 @@
+package proto
+
+import (
+	"testing"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestUnencryptedMessage_Encode(t *testing.T) {
+	d := UnencryptedMessage{
+		MessageID:   3401235567,
+		MessageData: []byte{1, 2, 3, 100, 112},
+	}
+	b := new(bin.Buffer)
+	if err := d.Encode(b); err != nil {
+		t.Fatal(err)
+	}
+	decoded := UnencryptedMessage{}
+	if err := decoded.Decode(b); err != nil {
+		t.Fatal(err)
+	}
+	require.Equal(t, d, decoded)
+	require.Zero(t, b.Len(), "buffer should be consumed")
+}