More docs and expand key_value_store example

src/handler/future.rs

@@ -0,0 +1,11 @@
+//! Handler future types.
+
+use http::Response;
+use std::convert::Infallible;
+use crate::body::BoxBody;
+
+opaque_future! {
+    /// The response future for [`IntoService`](super::IntoService).
+    pub type IntoServiceFuture =
+        futures_util::future::BoxFuture<'static, Result<Response<BoxBody>, Infallible>>;
+}