Support "caching" in the Dark language

[StachuDotNet]

I have this vague idea of a user being able to wrap a fn call with a 'cache' construct (maybe a new Expr, not sure), similar visually/ergonomically to feature flags. You have some place of setting how the cache works (e.g. the results expire after [x] timing, or the results expire after [x] usages, no expiry, etc.).

For example, let's say you have HTTP handlers that return the same results for the same inputs, but would cost a fair amount of processing time if handled in-line. It'd be great for the HTTP handler's body to be all/largely wrapped up in a 'cache' construct (again, I imagine this vaguely feeling like a feature flag) such that after the first request, subsequent responses are fast, without the Dark user having to manually deal with caching.

If this isn't clear, I can try to Figma for a few minutes how I imagine it looking.

[pbiggar]

Feels like a middleware?

[pbiggar]

A little bit like a python decorator, or like a lazy functionality