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/telegram/self_test.go

@@ -0,0 +1,29 @@
+package telegram
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+func TestClient_Self(t *testing.T) {
+	ctx := context.Background()
+	self, err := newTestClient(func(id int64, body bin.Encoder) (bin.Encoder, error) {
+		assert.IsType(t, &tg.UsersGetUsersRequest{}, body)
+		u := &tg.User{ID: 1}
+		u.SetBot(true)
+		return &tg.UserClassVector{
+			Elems: []tg.UserClass{u},
+		}, nil
+	}).Self(ctx)
+	require.NoError(t, err)
+
+	expected := &tg.User{ID: 1}
+	expected.SetBot(true)
+	require.Equal(t, expected, self)
+}