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/sub_conns.go

@@ -0,0 +1,29 @@
+package telegram
+
+import (
+	"context"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+)
+
+func (c *Client) invokeSub(ctx context.Context, dc int, input bin.Encoder, output bin.Decoder) error {
+	c.subConnsMux.Lock()
+
+	conn, ok := c.subConns[dc]
+	if ok {
+		c.subConnsMux.Unlock()
+		return conn.Invoke(ctx, input, output)
+	}
+
+	conn, err := c.dc(ctx, dc, 1, c.primaryDC(dc))
+	if err != nil {
+		c.subConnsMux.Unlock()
+		return errors.Wrapf(err, "create connection to DC %d", dc)
+	}
+	c.subConns[dc] = conn
+	c.subConnsMux.Unlock()
+
+	return conn.Invoke(ctx, input, output)
+}