feat: add QUIC transport to the chat example

[yellowred]

Description

See: #3501 (comment)

Notes & open questions

Removed development_transport and used a custom transport, since we don't want Quic in dev transport.
However, I anticipate others will copy this code to their new projects when they need Quic+Tcp, so there is a question of the purpose of the development_transport function.

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• A changelog entry has been made in the appropriate crates

[thomaseizinger]

Thank you! A few questions.

[thomaseizinger]

One request, other LGTM

[thomaseizinger]

Removed development_transport and used a custom transport, since we don't want Quic in dev transport.\nHowever, I anticipate others will copy this code to their new projects when they need Quic+Tcp, so there is a question of the purpose of the development_transport function.

It is a legitimate question. Personally, I think users should compose their transport for a production application themselves anyway.

But, it is useful to get started quickly.

Maybe we can incorporate this into SwarmBuilder somehow?

An idea sketch would be:

SwarmBuilder::new(local_peer_id)
   .tokio_executor()
   .default_transport()
   .behaviour(my_behaviour)
   .build()

The builder would be type-state guided such that you must call either default_transport or custom_transport(my_transport).

[yellowred]

But, it is useful to get started quickly.

Maybe we can incorporate this into SwarmBuilder somehow?

I like this idea. Everyone will be able to start quickly with a default and customize later on when they see a need for that.

[thomaseizinger]

The clippy build is failing due to a recent PR that merged into master (#3580), can you address that please?

[mxinden]

Idea above for a default_transport method on Swarm or an extension trait to Swarm sounds good to me. I don't have an opinion on the exact implementation of the mechanism. I do believe providing some default is valuable. Anecdotally just yesterday in the community call someone asked for the best defaults on a transport to get started.

[thomaseizinger]

Idea above for a default_transport method on Swarm or an extension trait to Swarm sounds good to me. I don't have an opinion on the exact implementation of the mechanism. I do believe providing some default is valuable. Anecdotally just yesterday in the community call someone asked for the best defaults on a transport to get started.

As you are pointing out, it would have to be an extension trait because libp2p-swarm does not pull in any specific transports. I'll open an issue.

[yellowred]

@thomaseizinger Added Quic as a separate crate.