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/vendored_keys.go

@@ -0,0 +1,58 @@
+package mtproto
+
+import (
+	// For embedding public keys.
+	_ "embed"
+	"sync"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/crypto"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/exchange"
+)
+
+var (
+	// publicKeys is byte blob of new keys added for PQInnerData encryption (key exchange).
+	//
+	// See https://github.com/telegramdesktop/tdesktop/commit/95a7ce4622dc24717dc5b95fc99599dddfd4ff6c.
+	//
+	// See https://github.com/tdlib/td/commit/e9e24282378fcdb3a3ce020bee4253b65ac98213.
+	//go:embed _data/public_keys.pem
+	publicKeys []byte
+
+	parsedKeys struct {
+		Keys []exchange.PublicKey
+		Once sync.Once
+	}
+)
+
+//nolint:gochecknoinits
+func init() {
+	makePublicKeys := func(data []byte) ([]exchange.PublicKey, error) {
+		rsaKeys, err := crypto.ParseRSAPublicKeys(data)
+		if err != nil {
+			return nil, err
+		}
+
+		keys := make([]exchange.PublicKey, 0, len(rsaKeys))
+		for _, key := range rsaKeys {
+			keys = append(keys, exchange.PublicKey{
+				RSA: key,
+			})
+		}
+		return keys, nil
+	}
+	parsedKeys.Once.Do(func() {
+		keys, err := makePublicKeys(publicKeys)
+		if err != nil {
+			panic(err)
+		}
+		parsedKeys.Keys = append(parsedKeys.Keys, keys...)
+	})
+}
+
+// vendoredKeys parses vendored file _data/public_keys.pem as list of
+// PEM-encoded public RSA keys.
+//
+// Most recent key list can be found on https://my.telegram.org/apps.
+func vendoredKeys() []exchange.PublicKey {
+	return parsedKeys.Keys
+}