Decorator formater

I would like a format decorator that takes a function so that you can format input to a standard

**Is your feature request related to a problem? Please describe.**
Network security rules accept per spec only Captital case protocol, ie '*' | 'Ah' | 'Esp' | 'Icmp' | 'Tcp' | 'Udp'.
Why can't i just add a `@format(x) => '${toUpper(substring(nsg.name, 0, 1))}${toLower(substring(nsg.name, 1, length(nsg.name) - 1))}')` to format the protocol from 'tcp' or 'TCP' to 'Tpc' etc.
This should also work on ints `@format(x => min(max(x, 20), 3)` eg **set** min 3 vmss instances but max 20 without error

**Describe the solution you'd like**
Please support 😄

The issue names no files, tests, or entry points. Start by turning the decorator examples into an agreed specification for string and integer formatting, including syntax, validation, and evaluation behavior; done means the scope and acceptance criteria are clear enough to implement and test.

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