[dl:http] fix setting 'mtime' per file (#7529)

introduce '_http_lastmodified' meta field

gallery_dl/downloader/http.py

@@ -322,7 +322,10 @@ class HttpDownloader(DownloaderBase):
 
         self.downloading = False
         if self.mtime:
-            kwdict.setdefault("_mtime", response.headers.get("Last-Modified"))
+            if "_http_lastmodified" in kwdict:
+                kwdict["_mtime"] = kwdict["_http_lastmodified"]
+            else:
+                kwdict["_mtime"] = response.headers.get("Last-Modified")
         else:
             kwdict["_mtime"] = None
 

gallery_dl/extractor/aryion.py

@@ -169,7 +169,7 @@ class AryionExtractor(Extractor):
                 "<p>", "</p>"), "", "")),
             "filename" : fname,
             "extension": ext,
-            "_mtime"   : lmod,
+            "_http_lastmodified": lmod,
         }