merge branch 'dt': move datetime utils into separate module

- use 'datetime.fromisoformat()' when possible (#7671)
- return a datetime-compatible object for invalid datetimes
  (instead of a 'str' value)

gallery_dl/extractor/reddit.py

@@ -57,7 +57,7 @@ class RedditExtractor(Extractor):
 
                 if submission:
                     submission["comment"] = None
-                    submission["date"] = text.parse_timestamp(
+                    submission["date"] = self.parse_timestamp(
                         submission["created_utc"])
                     yield Message.Directory, submission
                     visited.add(submission["id"])
@@ -124,7 +124,7 @@ class RedditExtractor(Extractor):
 
                         data = submission.copy()
                         data["comment"] = comment
-                        comment["date"] = text.parse_timestamp(
+                        comment["date"] = self.parse_timestamp(
                             comment["created_utc"])
 
                         if media: