Account for AFIT stabilization in 1.75.0 about async-trait

[hiroaki-yamamoto]

As far as I tried 1.75.0, the official async trait isn't object-safe for now while this crate is. This is the huge advantage of this crate when using Arc<dyn Trait + Send +Sync> style DI. This is why I'd like @dtolnay to keep maintaining this crate until the official async trait gets object-safe.

[thecaralice]

And here 1.75.0 is. Maybe consider writing a sentence or two on migrating.

[EstebanBorai]

Thanks so much to @dtolnay and contributors for this crate! This was so useful to have while waiting for this to happen!

[UkonnRa]

From official doc, users can use #[trait_variant::make] if they want to swap to AFIT?

From developer side, that's just migrate from one macro to another. I think I will still use #[async_macro] until all of my dependencies support the new feature?

[thecaralice]

@hiroaki-yamamoto

until the official async trait gets object-safe

This is unlikely to be possible without explicitly bounding Self: Sized in all of the RPITI methods, which prevents them from being accessible through a trait object