Bug: datetime fields not correctly parsed back to JSON-LD

[zigaklun]

There is a bug affecting the handling of datetime fields when parsing data back into JSON. In the CI tests, dateCreated and datePublished fields are being returned as Python datetime objects (e.g., datetime.datetime(2024, 3, 18, 0, 0)) rather than properly formatted JSON strings (e.g., '2024-03-18 00:00:00').

  -     'dateCreated': '2024-03-18 00:00:00',
  -     'datePublished': '2024-03-18 00:00:00',
  +     'dateCreated': datetime.datetime(2024, 3, 18, 0, 0),
  +     'datePublished': datetime.datetime(2024, 3, 18, 0, 0),

Currently, this issue causes CI tests to fail. To unblock progress, it was suggested to temporarily remove these fields from the test data, but a bug should be filed for proper resolution.

For reference look at the conversation in PR: #936