feat(registry): add sub_registry_with_labels

[popadi]

• Added sub_registry_with_labels method per discussion in Allow multiple labels in sub_registry_with_label method #144
• Updated the tests (which should be refactored or better documented I think, it's a bit hard to figure out the hierarchy or registries)

[popadi]

@mxinden any update/feedback on this?

[mxinden]

Change looks good to me. Thanks. Though now that we have sub_registry_with_labelS we can simply sub_registry_with_label, right? What do you think?

modified   src/registry.rs
@@ -239,11 +239,20 @@ impl Registry {
         &mut self,
         label: (Cow<'static, str>, Cow<'static, str>),
     ) -> &mut Self {
-        let mut labels = self.labels.clone();
-        labels.push(label);
+        self.sub_registry_with_labels(std::iter::once(label))
+    }
+
+    /// Like [`Registry::sub_registry_with_prefix`] but with multiple labels instead.
+    pub fn sub_registry_with_labels(
+        &mut self,
+        labels: impl Iterator<Item = (Cow<'static, str>, Cow<'static, str>)>,
+    ) -> &mut Self {
+        let mut new_labels = self.labels.clone();
+        new_labels.extend(labels);
+
         let sub_registry = Registry {
             prefix: self.prefix.clone(),
-            labels,
+            labels: new_labels,
             ..Default::default()
         };

[popadi]

Change looks good to me. Thanks. Though now that we have sub_registry_with_labelS we can simply sub_registry_with_label, right? What do you think?

Thanks for the suggestion! I updated the code.
Tests might need some extra work (I think individual tests per method would also be useful, alongside the existing one), but I will probably do that in a separate pull request.

[mxinden]

Thanks for the follow-ups.