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/dcs/resolver.go

@@ -0,0 +1,28 @@
+package dcs
+
+import (
+	"context"
+	"net"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/transport"
+)
+
+var _ Resolver = DefaultResolver()
+
+// Resolver resolves DC and creates transport MTProto connection.
+type Resolver interface {
+	Primary(ctx context.Context, dc int, list List) (transport.Conn, error)
+	MediaOnly(ctx context.Context, dc int, list List) (transport.Conn, error)
+	CDN(ctx context.Context, dc int, list List) (transport.Conn, error)
+}
+
+// DialFunc connects to the address on the named network.
+type DialFunc func(ctx context.Context, network, addr string) (net.Conn, error)
+
+// Protocol is MTProto transport protocol.
+//
+// See https://core.telegram.org/mtproto/mtproto-transports
+type Protocol interface {
+	Codec() transport.Codec
+	Handshake(conn net.Conn) (transport.Conn, error)
+}