Metadata support

[sergiimk]

Example:

    #[derive(Debug)]
    struct EventHandlerDesc {
        event_type: &'static str,
    }

    trait EventHandler: Send + Sync {
        fn on_event(&self, event: &str) -> String;
    }

    #[dill::component]
    #[dill::interface(dyn EventHandler)]
    #[dill::meta(EventHandlerDesc { event_type: "A"})]
    struct EventHandlerA;
    impl EventHandler for EventHandlerA {
      ...
    }

    #[dill::component]
    #[dill::interface(dyn EventHandler)]
    #[dill::meta(EventHandlerDesc { event_type: "B"})]
    struct EventHandlerB;
    impl EventHandler for EventHandlerB {
      ...
    }

    #[dill::component]
    #[dill::interface(dyn EventHandler)]
    #[dill::meta(EventHandlerDesc { event_type: "A"})]
    #[dill::meta(EventHandlerDesc { event_type: "B"})]
    struct EventHandlerAB;
    impl EventHandler for EventHandlerAB {
      ...
    }


// Usage
catalog.builders_for_with_meta::<dyn EventHandler, _>(
  |desc: &EventHandlerDesc| desc.event_type == "B"
)

[s373r]

LGMT with a minor comment + please update CHANGELOG.md

[zaychenko-sergei]

Noticing linear search at runtime to apply the filter, but that's fine. This is better than constructing objects from builders to filter.