add derive + docs

src/model/valid.rs

@@ -1,7 +1,7 @@
 /// This trait allows a `Model` to be validated.
 pub trait Validate {
     /// Validate the `Model`
-    async fn validate(&self) -> bool;
+    fn validate(&self) -> impl std::future::Future<Output = bool> + Send;
 }
 
 /// Validate a value and return `false` if validation fails.