Add request id example

[conways-glider]

Add a request-id example using tower, tower-http, and tracing.

Motivation

This is something I've had to do a few times now in axum that I had to figure out through a combination of axum docs and tower-http docs. Having a concrete example shows a way of doing this in a way that axum supports without having to dig through 2 docs.rs pages (or 3 if you're looking in tower as well).

Figuring out the middleware, the order, and how to write the TraceLayer to avoid extra clones has prevented issues for other engineers I've interacted with as well, so the goal is also to clarify an easy way to achieve request ids.

Solution

• Add an example of how to add randomized request ids at examples/request-id.
• Utilize tower and tower-http crates to handle request-id middleware.
• Use tracing and tracing-subscriber crates to show how to add these request ids to each requests span.

[mladedav]

Thanks