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/downloader/web.go

@@ -0,0 +1,38 @@
+package downloader
+
+import (
+	"context"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+var errHashesNotSupported = errors.New("this schema does not support hashes fetch")
+
+// web is a web file download schema.
+// See https://core.telegram.org/api/files#downloading-webfiles.
+type web struct {
+	client Client
+
+	location tg.InputWebFileLocationClass
+}
+
+var _ schema = web{}
+
+func (w web) Chunk(ctx context.Context, offset int64, limit int) (chunk, error) {
+	file, err := w.client.UploadGetWebFile(ctx, &tg.UploadGetWebFileRequest{
+		Location: w.location,
+		Offset:   int(offset),
+		Limit:    limit,
+	})
+	if err != nil {
+		return chunk{}, err
+	}
+
+	return chunk{data: file.Bytes, tag: file.FileType}, nil
+}
+
+func (w web) Hashes(ctx context.Context, offset int64) ([]tg.FileHash, error) {
+	return nil, errHashesNotSupported
+}