feat: middleware (WIP)

Cargo.toml

@@ -21,3 +21,4 @@ thiserror = "2"
 http-body-util = "0.1.1"
 chrono = { version = "0.4", features = ["clock"] }
 reqwest = { version = "0.12", features = ["json", "rustls-tls", "gzip"], default-features = false }
+hashbrown = { version = "0.16", features = ["serde"] }