Feature request: adding extra fields support like Identity on the workitem cards

Hello,

Thank you for the quick response to my bug report. When I using your plugin, we want to add the Created by field into the workitem card though the configration you provided. However, the Created by is a Identity type field which does not supported. Would you like to add the support for this field? Much appreciations on this.

Additionally, It is much better that Assignee on the card could be removed with an option.

Thanks again.