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/mtproto/rpc.go

@@ -0,0 +1,71 @@
+package mtproto
+
+import (
+	"context"
+
+	"github.com/go-faster/errors"
+	"go.uber.org/zap"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/mt"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/rpc"
+)
+
+// Invoke sends input and decodes result into output.
+//
+// NOTE: Assuming that call contains content message (seqno increment).
+func (c *Conn) Invoke(ctx context.Context, input bin.Encoder, output bin.Decoder) error {
+	msgID, seqNo := c.nextMsgSeq(true)
+	req := rpc.Request{
+		MsgID:  msgID,
+		SeqNo:  seqNo,
+		Input:  input,
+		Output: output,
+	}
+
+	log := c.log.With(
+		zap.Int64("msg_id", req.MsgID),
+	)
+	log.Debug("Invoke start")
+	defer log.Debug("Invoke end")
+
+	if err := c.rpc.Do(ctx, req); err != nil {
+		var badMsgErr *badMessageError
+		if errors.As(err, &badMsgErr) && badMsgErr.Code == codeIncorrectServerSalt {
+			// Should retry with new salt.
+			c.log.Debug("Setting server salt")
+			// Store salt from server.
+			c.storeSalt(badMsgErr.NewSalt)
+			// Reset saved salts to fetch new.
+			c.salts.Reset()
+			c.log.Info("Retrying request after basMsgErr", zap.Int64("msg_id", req.MsgID))
+			return c.rpc.Do(ctx, req)
+		}
+		return err
+	}
+
+	return nil
+}
+
+func (c *Conn) dropRPC(req rpc.Request) error {
+	ctx, cancel := context.WithTimeout(context.Background(),
+		c.getTimeout(mt.RPCDropAnswerRequestTypeID),
+	)
+	defer cancel()
+
+	var resp mt.RPCDropAnswerBox
+	if err := c.Invoke(ctx, &mt.RPCDropAnswerRequest{
+		ReqMsgID: req.MsgID,
+	}, &resp); err != nil {
+		return err
+	}
+
+	switch resp.RpcDropAnswer.(type) {
+	case *mt.RPCAnswerDropped, *mt.RPCAnswerDroppedRunning:
+		return nil
+	case *mt.RPCAnswerUnknown:
+		return errors.New("answer unknown")
+	default:
+		return errors.Errorf("unexpected response type: %T", resp.RpcDropAnswer)
+	}
+}