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/tgtest/cluster/dispatch.go

@@ -0,0 +1,70 @@
+package cluster
+
+import (
+	"crypto/rsa"
+
+	"go.uber.org/zap"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/crypto"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/exchange"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tgtest"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tgtest/services"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/transport"
+)
+
+// Common returns common dispatcher.
+func (c *Cluster) Common() *tgtest.Dispatcher {
+	return c.common
+}
+
+func (c *Cluster) getCodec() (codec func() transport.Codec) {
+	if !c.web {
+		codec = c.protocol.Codec
+	}
+	return codec
+}
+
+// DC registers new server and returns it.
+func (c *Cluster) DC(id int, name string) (*tgtest.Server, *tgtest.Dispatcher) {
+	if s, ok := c.setups[id]; ok {
+		return s.srv, s.dispatch
+	}
+
+	key, err := rsa.GenerateKey(c.random, crypto.RSAKeyBits)
+	if err != nil {
+		// TODO(tdakkota): Return error instead.
+		panic(err)
+	}
+	privateKey := exchange.PrivateKey{
+		RSA: key,
+	}
+
+	d := tgtest.NewDispatcher()
+	server := tgtest.NewServer(privateKey, tgtest.UnpackInvoke(d), tgtest.ServerOptions{
+		DC:     id,
+		Logger: c.log.Named(name).With(zap.Int("dc_id", id)),
+		Codec:  c.getCodec(),
+	})
+	c.setups[id] = setup{
+		srv:      server,
+		dispatch: d,
+	}
+	c.keys = append(c.keys, server.Key())
+
+	// We set server fallback handler to dispatch request in order
+	// 1) Explicit DC handler
+	// 2) Explicit common handler
+	// 3) Common fallback
+	d.Fallback(c.Common())
+	return server, d
+}
+
+// Dispatch registers new server and returns its dispatcher.
+func (c *Cluster) Dispatch(id int, name string) *tgtest.Dispatcher {
+	_, d := c.DC(id, name)
+	return d
+}
+
+func (c *Cluster) fallback() tgtest.HandlerFunc {
+	return services.NotImplemented
+}