fix: honor allow attributes on interface methods

[ivov]

Honor #[allow(unused_value)] on interface method declarations so that fluent-chain interfaces stop tripping lint.unused_value at every call site.

let api = app.Group("/api/v1")
api.Get("/ping", |c| c.SendString("pong"))
api.Post("/echo", |c| c.SendString("echo"))

Previously, every line warned and had to be wrapped with let _ = ...

[github-actions]

Released in lisette-v0.2.4