uuid, date & time substitution in step parameters

[derdualist]

it should be possible to use step parameters, that have dynamic values like UUIDs and time.

Examples:

* Type "user.!{uuid}@mail.com"
// user.80b73bed-9330-4301-a3e0-f535111678f7@mail.com
* Type "user.!{time}@mail.com"
// user.2023-10-19T12:33:30.000@mail.com
* Type "user.!{time:%Y%%m%dT%H:%M:%S}@mail.com"
// user.2023-10-19T12:33:30@mail.com"

The time substitute can have an optional formatting string, as it is defined in Python's language doc: https://docs.python.org/3/library/datetime.html#strftime-and-strptime-format-codes

TBD: Time Zone options.