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/write.go

@@ -0,0 +1,57 @@
+package mtproto
+
+import (
+	"context"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+)
+
+func (c *Conn) writeContentMessage(ctx context.Context, msgID int64, seqNo int32, message bin.Encoder) error {
+	return c.write(ctx, msgID, seqNo, message)
+}
+
+func (c *Conn) writeServiceMessage(ctx context.Context, message bin.Encoder) error {
+	msgID, seqNo := c.nextMsgSeq(false)
+	return c.write(ctx, msgID, seqNo, message)
+}
+
+var bufPool = bin.NewPool(0)
+
+func (c *Conn) write(ctx context.Context, msgID int64, seqNo int32, message bin.Encoder) error {
+	// Grab shared lock for writing.
+	// It prevents message sending during key regeneration if server forgot current auth key.
+	c.exchangeLock.RLock()
+	defer c.exchangeLock.RUnlock()
+
+	b := bufPool.Get()
+	defer bufPool.Put(b)
+
+	if err := c.newEncryptedMessage(msgID, seqNo, message, b); err != nil {
+		return err
+	}
+
+	if err := c.conn.Send(ctx, b); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *Conn) nextMsgSeq(content bool) (msgID int64, seqNo int32) {
+	c.reqMux.Lock()
+	defer c.reqMux.Unlock()
+
+	msgID = c.newMessageID()
+
+	// Computing current sequence number (seqno).
+	// This should be serialized with new message id generation.
+	//
+	// See https://github.com/gotd/td/issues/245 for reference.
+	seqNo = c.sentContentMessages * 2
+	if content {
+		seqNo++
+		c.sentContentMessages++
+	}
+
+	return
+}