feat: allow patterns

[erwanncloarec]

This is a proposal to resolve the following issue:

• Allow patterns #85

This is my first contribution, please let me know if there's anything I can do 🙏

I tested on a small project like this:

let (prometheus_layer, metric_handle) = PrometheusMetricLayerBuilder::new()
        .with_default_metrics()
        .with_allow_patterns(&["/hello", "/hola", "/hi", "/hi/hi", "/hi/{other}"])
        .with_group_patterns_as("/hi", &["/hi/hi", "/hi/{other}"])
        .build_pair();

    // Build our application with a route and the metrics endpoint
    let router = Router::new()
        .route("/hello", get(hello_world))
        .route("/hola", get(hello_world))
        .route("/hi", get(hello_world))
        .route("/hi/hi", get(hello_world))
        .route("/hi/{other}", get(hello_world))
        .route("/metrics", get(|| async move { metric_handle.render() }))
        .layer(ServiceBuilder::new().layer(prometheus_layer));

With the following calls:

#!/bin/sh

curl localhost:8000/hello
curl localhost:8000/hello
curl localhost:8000/hello
curl localhost:8000/hola
curl localhost:8000/hola
curl localhost:8000/hi
curl localhost:8000/hi/hi
curl localhost:8000/hi/tomato

curl localhost:8000/.aws/credentials
curl localhost:8000/.aws/credentials
curl localhost:8000/.aws/credentials
curl localhost:8000/sqdokqsdk
curl localhost:8000/:sqdqsd
curl localhost:8000/azerty

I've got those metrics:

[Ptrskay3]

Thanks, looks good from first glance. I'll probably have to time review it properly this weekend.

[Ptrskay3]

Just a nit, but looks good. Thanks!

Do you want to add this to the changelog as well?