Rework error handling example

[davidpdrsn]

This reworks the ye olde error-handling-and-dependency-injection. I've removed all the dependency injection bits because I think they're distracting and deserve their own example.

Hopefully this new version is easier to follow and can serve as a template for people to build upon.

[jplatte]

As-is, the uri (and method) won't be in quotes but the matched path will, as the comment at the start of the file shows correctly. I find this pretty weird. Maybe use let uri = req.uri().to_string(); above instead, and remove the % before uri here? For the method, it probably makes sense for it not to be in quotes.

[jplatte]

Maybe controversial, but I find the err= bit in the output a bit weird. IMHO tracing fields are much more useful for fields whose exact value you'd want to match when searching logs, rather than error messages that are generally just searched for specific keywords.

Suggested change

	tracing::error!(%err, "error from time_library");
	tracing::error!("error from time_library: {err}");

[NVedsted]

Not sure what the chances are of me stumbling upon links to the deleted example just as this merges, haha. I just wanted to highlight these references to the deleted/renamed file:

• axum/axum/src/docs/error_handling.md

  Lines 46 to 49 in 5d388c8

  	* [`error-handling-and-dependency-injection`][ehdi] for application-specific detailed errors
  	[anyhow]: https://github.com/tokio-rs/axum/blob/main/examples/anyhow-error-response/src/main.rs
  	[ehdi]: https://github.com/tokio-rs/axum/blob/main/examples/error-handling-and-dependency-injection/src/main.rs

• axum/axum/src/handler/mod.rs

  Lines 40 to 43 in 5d388c8

  	//! * [`error-handling-and-dependency-injection`][ehdi] for application-specific detailed errors
  	//!
  	//! [anyhow]: https://github.com/tokio-rs/axum/blob/main/examples/anyhow-error-response/src/main.rs
  	//! [ehdi]: https://github.com/tokio-rs/axum/blob/main/examples/error-handling-and-dependency-injection/src/main.rs

Not familiar with contributing, so let me know if an issue would be preferable. :)

[davidpdrsn]

Thanks for noticing! I've filed an issue #2464