Make StatefulListener::new a little more convinient

Remove `timeout_hint` from the `StatefulListener::new` function. This parameter
is confusing and is likely to be set to `None` in most cases.

Add a `StatefulListener::new_with_timeout_hint` parameter which is the same as
the old `StatefulListener::new`.

examples/heroku_ping_pong_bot/src/main.rs

@@ -62,7 +62,7 @@ pub async fn webhook(bot: AutoSend<Bot>) -> impl update_listeners::UpdateListene
 
     fn streamf<S, T>(state: &mut (S, T)) -> &mut S { &mut state.0 }
     
-    StatefulListener::new((stream, stop_token), streamf, |state: &mut (_, AsyncStopToken)| state.1.clone(), None::<for<'a> fn(&'a _) -> _>)
+    StatefulListener::new((stream, stop_token), streamf, |state: &mut (_, AsyncStopToken)| state.1.clone())
 }
 
 async fn run() {

examples/ngrok_ping_pong_bot/src/main.rs

@@ -54,7 +54,7 @@ pub async fn webhook(bot: AutoSend<Bot>) -> impl update_listeners::UpdateListene
 
     fn streamf<S, T>(state: &mut (S, T)) -> &mut S { &mut state.0 }
     
-    StatefulListener::new((stream, stop_token), streamf, |state: &mut (_, AsyncStopToken)| state.1.clone(), None::<for<'a> fn(&'a _) -> _>)
+    StatefulListener::new((stream, stop_token), streamf, |state: &mut (_, AsyncStopToken)| state.1.clone())
 }
 
 async fn run() {

src/dispatching/update_listeners/stateful_listener.rs

@@ -39,9 +39,21 @@ pub struct StatefulListener<St, Assf, Sf, Thf> {
     pub timeout_hint: Option<Thf>,
 }
 
+impl<St, Assf, Sf> StatefulListener<St, Assf, Sf, for<'a> fn(&'a St) -> Option<Duration>> {
+    /// Creates new stateful listener from it's components.
+    pub fn new(state: St, stream: Assf, stop_token: Sf) -> Self {
+        Self { state, stream, stop_token, timeout_hint: None }
+    }
+}
+
 impl<St, Assf, Sf, Thf> StatefulListener<St, Assf, Sf, Thf> {
     /// Creates new stateful listener from it's components.
-    pub fn new(state: St, stream: Assf, stop_token: Sf, timeout_hint: Option<Thf>) -> Self {
+    pub fn new_with_timeout_hint(
+        state: St,
+        stream: Assf,
+        stop_token: Sf,
+        timeout_hint: Option<Thf>,
+    ) -> Self {
         Self { state, stream, stop_token, timeout_hint }
     }
 }