feat: add shared API operation metadata macro

crates/api-macros/tests/ui/private_body.rs

@@ -0,0 +1,14 @@
+#![allow(async_fn_in_trait, private_interfaces)]
+
+use api_macros::api;
+
+struct PrivateRequest;
+pub struct Response;
+
+#[api]
+pub trait PrivateBody {
+    #[post("/widgets")]
+    async fn create(&self, #[body] request: PrivateRequest) -> Response;
+}
+
+fn main() {}