Since we are heavily using tokio and reqwest, it would be more sensible to use an asynchronous web framework rather than a blocking one.

Migrating to axum will have the following benefits too:

• It's easier to maintain the API than the macro.
• Remove some old future-incompatibile deps:

warning: the following packages contain code that will be rejected by a future version of Rust: buf_redux v0.8.4, multipart v0.18.0
note: to see what the problems were, use the option `--future-incompat-report`, or run `cargo report future-incompatibilities --id 1`