list_ticker_news misuses published_utc.* values #391

Describe the bug

Controlling the published_utc parameter requires passing le/ge filters as e.g. published_utc.gt. However, the python library passes them incorrectly as published.utc_gt. This makes the backend HTTP API to ignore the parameter as whole, as it does not recognize it.

To Reproduce
Simply use any of the documented published_utc_gt type of input parameters through the RESTClient::list_ticker_news().