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/auth/qrlogin/token.go

@@ -0,0 +1,76 @@
+package qrlogin
+
+import (
+	"encoding/base64"
+	"image"
+	"net/url"
+	"time"
+
+	"github.com/go-faster/errors"
+	"rsc.io/qr"
+)
+
+// Token represents Telegram QR Login token.
+type Token struct {
+	token   []byte
+	expires time.Time
+}
+
+// ParseTokenURL creates Token from given URL.
+func ParseTokenURL(u string) (Token, error) {
+	parsed, err := url.Parse(u)
+	if err != nil {
+		return Token{}, err
+	}
+	switch {
+	case parsed.Scheme != "tg":
+		return Token{}, errors.Errorf("unexpected scheme %q", parsed.Scheme)
+	case parsed.Host != "login":
+		return Token{}, errors.Errorf("wrong path %q", parsed.Host)
+	}
+
+	q := parsed.Query()
+	if q.Get("token") == "" {
+		return Token{}, errors.New("token is empty")
+	}
+	token, err := base64.URLEncoding.DecodeString(q.Get("token"))
+	if err != nil {
+		return Token{}, err
+	}
+
+	return NewToken(token, 0), nil
+}
+
+// NewToken creates new Token.
+func NewToken(token []byte, expires int) Token {
+	return Token{
+		token:   token,
+		expires: time.Unix(int64(expires), 0),
+	}
+}
+
+// Expires returns token expiration time.
+func (t Token) Expires() time.Time {
+	return t.expires
+}
+
+// String implements fmt.Stringer.
+func (t Token) String() string {
+	return base64.URLEncoding.EncodeToString(t.token)
+}
+
+// URL returns login URL.
+//
+// See https://core.telegram.org/api/qr-login#exporting-a-login-token.
+func (t Token) URL() string {
+	return "tg://login?token=" + base64.URLEncoding.EncodeToString(t.token)
+}
+
+// Image returns QR image.
+func (t Token) Image(level qr.Level) (image.Image, error) {
+	code, err := qr.Encode(t.URL(), level)
+	if err != nil {
+		return nil, errors.Wrap(err, "encode")
+	}
+	return code.Image(), nil
+}