[instagram] fix highlights extraction (#2197)

* [instagram] fix highlights extraction

* [instagram] improve highlights extraction

- 'yield' individual reels instead of collecting them in a list
  and returning them all at once
- reduce 'chunk_size' to an even saver value
  (instagram.com also uses 5)

gallery_dl/extractor/instagram.py

@@ -748,13 +748,19 @@ def posts(self):
 
         endpoint = "/v1/highlights/{}/highlights_tray/".format(user["id"])
         tray = self._request_api(endpoint)["tray"]
-
         reel_ids = [highlight["id"] for highlight in tray]
+
+        # Anything above 30 responds with statuscode 400.
+        # 30 can work, however, sometimes the API will respond with 560 or 500.
+        chunk_size = 5
         endpoint = "/v1/feed/reels_media/"
-        params = {"reel_ids": reel_ids}
-        reels = self._request_api(endpoint, params=params)["reels"]
 
-        return [reels[rid] for rid in reel_ids]
+        for offset in range(0, len(reel_ids), chunk_size):
+            chunk_ids = reel_ids[offset : offset+chunk_size]
+            params = {"reel_ids": chunk_ids}
+            reels = self._request_api(endpoint, params=params)["reels"]
+            for reel_id in chunk_ids:
+                yield reels[reel_id]
 
 
 class InstagramReelsExtractor(InstagramExtractor):