[ard] Fix valid URL

Partial fix for #2975

yt_dlp/extractor/ard.py

@@ -407,8 +407,9 @@ class ARDBetaMediathekIE(ARDMediathekBaseIE):
         (?:(?:beta|www)\.)?ardmediathek\.de/
         (?:(?P<client>[^/]+)/)?
         (?:player|live|video|(?P<playlist>sendung|sammlung))/
-        (?:(?P<display_id>[^?#]+)/)?
-        (?P<id>(?(playlist)|Y3JpZDovL)[a-zA-Z0-9]+)'''
+        (?:(?P<display_id>(?(playlist)[^?#]+?|[^?#]+))/)?
+        (?P<id>(?(playlist)|Y3JpZDovL)[a-zA-Z0-9]+)
+        (?(playlist)/(?P<season>\d+)?/?(?:[?#]|$))'''
 
     _TESTS = [{
         'url': 'https://www.ardmediathek.de/mdr/video/die-robuste-roswita/Y3JpZDovL21kci5kZS9iZWl0cmFnL2Ntcy84MWMxN2MzZC0wMjkxLTRmMzUtODk4ZS0wYzhlOWQxODE2NGI/',
@@ -436,6 +437,13 @@ class ARDBetaMediathekIE(ARDMediathekBaseIE):
             'description': 'md5:39578c7b96c9fe50afdf5674ad985e6b',
             'upload_date': '20211108',
         },
+    }, {
+        'url': 'https://www.ardmediathek.de/sendung/beforeigners/beforeigners/staffel-1/Y3JpZDovL2Rhc2Vyc3RlLmRlL2JlZm9yZWlnbmVycw/1',
+        'playlist_count': 6,
+        'info_dict': {
+            'id': 'Y3JpZDovL2Rhc2Vyc3RlLmRlL2JlZm9yZWlnbmVycw',
+            'title': 'beforeigners/beforeigners/staffel-1',
+        },
     }, {
         'url': 'https://beta.ardmediathek.de/ard/video/Y3JpZDovL2Rhc2Vyc3RlLmRlL3RhdG9ydC9mYmM4NGM1NC0xNzU4LTRmZGYtYWFhZS0wYzcyZTIxNGEyMDE',
         'only_matching': True,
@@ -561,14 +569,15 @@ class ARDBetaMediathekIE(ARDMediathekBaseIE):
                 break
             pageNumber = pageNumber + 1
 
-        return self.playlist_result(entries, playlist_title=display_id)
+        return self.playlist_result(entries, playlist_id, playlist_title=display_id)
 
     def _real_extract(self, url):
-        video_id, display_id, playlist_type, client = self._match_valid_url(url).group(
-            'id', 'display_id', 'playlist', 'client')
+        video_id, display_id, playlist_type, client, season_number = self._match_valid_url(url).group(
+            'id', 'display_id', 'playlist', 'client', 'season')
         display_id, client = display_id or video_id, client or 'ard'
 
         if playlist_type:
+            # TODO: Extract only specified season
             return self._ARD_extract_playlist(url, video_id, display_id, client, playlist_type)
 
         player_page = self._download_json(