fix: make the light protocols return a Send future, resolving the warning that async fn in trait definitions is discouraged

protocol/src/light.rs

@@ -1,22 +1,22 @@
-use std::error::Error;
+use std::{error::Error, future::Future};
 
 use deranged::RangedU16;
 
 pub trait Light {
     type IsOnError: Error;
-    async fn is_on(&self) -> Result<bool, Self::IsOnError>;
+    fn is_on(&self) -> impl Future<Output = Result<bool, Self::IsOnError>> + Send;
 
     type IsOffError: Error;
-    async fn is_off(&self) -> Result<bool, Self::IsOffError>;
+    fn is_off(&self) -> impl Future<Output = Result<bool, Self::IsOffError>> + Send;
 
     type TurnOnError: Error;
-    async fn turn_on(&mut self) -> Result<(), Self::TurnOnError>;
+    fn turn_on(&mut self) -> impl Future<Output = Result<(), Self::TurnOnError>> + Send;
 
     type TurnOffError: Error;
-    async fn turn_off(&mut self) -> Result<(), Self::TurnOffError>;
+    fn turn_off(&mut self) -> impl Future<Output = Result<(), Self::TurnOffError>> + Send;
 
     type ToggleError: Error;
-    async fn toggle(&mut self) -> Result<(), Self::ToggleError>;
+    fn toggle(&mut self) -> impl Future<Output = Result<(), Self::ToggleError>> + Send;
 }
 
 #[derive(Debug, Clone, Copy, derive_more::From, derive_more::Into)]
@@ -24,7 +24,10 @@ pub struct Kelvin(pub RangedU16<2000, 10000>);
 
 pub trait KelvinLight: Light {
     type TurnToKelvinError: Error;
-    async fn turn_to_kelvin(&mut self, temperature: Kelvin) -> Result<(), Self::TurnToKelvinError>;
+    fn turn_to_kelvin(
+        &mut self,
+        temperature: Kelvin,
+    ) -> impl Future<Output = Result<(), Self::TurnToKelvinError>> + Send;
 }
 
 // TODO: replace with a type from a respected and useful library
@@ -33,5 +36,8 @@ pub struct Rgb(pub u8, pub u8, pub u8);
 
 pub trait RgbLight: Light {
     type TurnToRgbError: Error;
-    async fn turn_to_rgb(&mut self, color: Rgb) -> Result<(), Self::TurnToRgbError>;
+    fn turn_to_rgb(
+        &mut self,
+        color: Rgb,
+    ) -> impl Future<Output = Result<(), Self::TurnToRgbError>> + Send;
 }