Ability to return errors from middleware

[justhaug]

I have looked for existing issues (including closed) about this

Feature Request

I essentially want to have a middleware that doesn't send back a response or status code at all. Something like one of towers layers which load shed or do filters (which doesn't work because Layers must have Infallible responses).

Motivation

The reason for this is to immediately get rid of malicious requests with as little compute as possible.

Proposal

No idea if this should be included in axum considering what is written here and I am not familiar enough with the internals of axum to know if it can be implemented without changing lots of traits.

Alternatives

I can just return a response without a body, this issue isn't a blocker. Feel free to close if it doesn't align with axum's current approach.