Why is not possible to create tickets with custom date/times via FreshDesk API? I'm trying to migrate existing tickets from an external platform to FreshDesk and it is essential to have the correct creation date/time for each ticket and conversation. 

Right now all tickets are being created with the current date/time and adding the "created_at" field to the call returns a validation error:

{"description":"Validation failed","errors":"{"field":"created_at","message":"Unexpected/invalid field in request","code":"invalid_field"}]}

Is this a plan limitation? I'm on Sprout plan now. If I upgrade to a paid plan, will this restriction be removed? 

I've found this related topic from 5 years ago, but there's no recent response:

https://support.freshdesk.com/support/discussions/topics/21687

Any help is appreciated. Thanks!