[extractor] Allow `http_headers` to be specified for `thumbnails`

yt_dlp/YoutubeDL.py

@@ -3860,7 +3860,7 @@ class YoutubeDL(object):
             else:
                 self.to_screen(f'[info] Downloading {thumb_display_id} ...')
                 try:
-                    uf = self.urlopen(t['url'])
+                    uf = self.urlopen(sanitized_Request(t['url'], headers=t.get('http_headers', {})))
                     self.to_screen(f'[info] Writing {thumb_display_id} to: {thumb_filename}')
                     with open(encodeFilename(thumb_filename), 'wb') as thumbf:
                         shutil.copyfileobj(uf, thumbf)

yt_dlp/extractor/common.py

@@ -239,6 +239,7 @@ class InfoExtractor(object):
                         * "resolution" (optional, string "{width}x{height}",
                                         deprecated)
                         * "filesize" (optional, int)
+                        * "http_headers" (dict) - HTTP headers for the request
     thumbnail:      Full URL to a video thumbnail image.
     description:    Full video description.
     uploader:       Full name of the video uploader.
@@ -272,6 +273,8 @@ class InfoExtractor(object):
                         * "url": A URL pointing to the subtitles file
                     It can optionally also have:
                         * "name": Name or description of the subtitles
+                        * http_headers: A dictionary of additional HTTP headers
+                                  to add to the request.
                     "ext" will be calculated from URL if missing
     automatic_captions: Like 'subtitles'; contains automatically generated
                     captions instead of normal subtitles