static-metric/src/builder: Allow non-public label enums

[mxinden]

Imagine the following static metric generation:

make_static_metric! {
    label_enum Methods {
        post,
        get,
    }

    struct MyStaticCounterVec: Counter {
        "method" => Methods,
    }
}

This will roughly expand to:

enum Methods {
    post,
    get,
}

use self::prometheus_static_scope_0::MyStaticCounterVec;
mod prometheus_static_scope_0 {
    pub struct MyStaticCounterVec {
        pub post: MyStaticCounterVec2,
        pub get: MyStaticCounterVec2,
    }
}

Rustc would complain that the private type 'Methods' [is] in [the] public interface (error E0446) MyStaticCounterVec.

There is no reason for MyStaticCounterVec to be defined with visibility pub. This commit instead defines MyStaticCounterVec with pub(super) and thus MyStaticCounterVec does not expose the private type Methods.

Signed-off-by: Max Inden [email protected]

[breezewish]

Maybe supplying some tests that will pass compile in this PR but will fail in master would be better!