Update Axum to 0.8

[RemiBardon]

I tried to update Axum to 0.8, but because of the removal of async_trait in https://github.com/tokio-rs/axum/releases/tag/axum-core-v0.5.0 it doesn't work.

When JosephLenton/axum-test#131 will be merged and released, we'll be able to remove all #[async_trait]s, replace /:params by /{param}s everywhere and the code should compile.

See tokio-rs/axum#2308, https://tokio.rs/blog/2025-01-01-announcing-axum-0-8-0#async_trait-removal and Eugeny/russh#236.

[JosephLenton]

Hey @RemiBardon , Axum Test has now been updated to Axum 8. You can find this released as v17.0.0.

[RemiBardon]

@JosephLenton Nice thanks!