Provide uuid macro without dependencies

[Nugine]

I'm submitting a feature

Description

#556 (comment)

Related Issue(s)

resolves #556

[KodrAus]

cc @QnnOkabayashi

[QnnOkabayashi]

At this point, we should change the feature gate to something like "macro-diagnostics". I also personally think that it should be on by default and require opting-out, since nice error messages should be the default. Thoughts?

[KodrAus]

A macro-diagnostics feature sounds like a good one to me 👍 Ideally we would have it on by default, but unfortunately for a non-trivial subset of users any additional dependencies will be pushed back against. That's one of our main reasons for a non-proc-macro version, and is also what landed us with a fast-rng feature that pulls in rand. I think there's an alternative approach to default features though that we can take: recommend a set of features to enable at the top of the README and in the crate-level docs:

[dependencies.uuid]
version = "1"
features = [
    "v4",                # allow generating random UUIDs
    "fast-rng",          # use a faster (but still sufficiently random) algorithm
    "macro-diagnostics", # support more detailed diagnostics in the `uuid!` macro
]

It's not on by default, but it's recommended by default.

[KodrAus]

Thanks @Nugine! This looks good to me. I just had one suggestion on a missed feature rename in the docs.