Error in generating key pair for unified license

Bugs found in key pair generation:
field valid_to and valid_from has conflict in return date value.
field valid_to received data from license_expiry date and has value of Date string, field valid_from is Date type generate from typescript code. so when it is different of string type when key is generate and the the format javascript translate the Date format (ISO 8601) 
Solution: return 2 fields into string value and has the format of DATE, can be datetime/timestamp in the future.