env: attempt to parse nested configuration

we use nested toml tables in our configuration, one table per what we think to be a logical section. However, because we want to add environment variables as configuration sources, we have to be able to parse nested dictionaries.
In order to do that, beside just using .prefix to filter out variables which don't concern us, we must also split the string of the variable name in keys, and for that we try to use the .split method

odilia/src/main.rs

@@ -91,14 +91,11 @@ async fn main() -> eyre::Result<()> {
 	// Otherwise create it in XDG_CONFIG_HOME
 	//default configuration first, because that doesn't affect the priority outlined above
 	let figment = Figment::from(Serialized::defaults(ApplicationConfig::default()))
-	//environment variables
-	.join(Env::prefixed("ODILIA_"));
+		//environment variables
+		.join(Env::prefixed("ODILIA_").split("_"));
 	//cli override, if applicable
-	let figment = if let Some(path) = args.config {
-		figment.join(Toml::file(path))
-	} else {
-		figment
-	};
+	let figment =
+		if let Some(path) = args.config { figment.join(Toml::file(path)) } else { figment };
 	//create a config.toml file in `XDG_CONFIG_HOME`, to make it possible for the user to edit the default values, if it doesn't exist already
 	let xdg_dirs = xdg::BaseDirectories::with_prefix("odilia").expect(
 			"unable to find the odilia config directory according to the xdg dirs specification",
@@ -121,7 +118,7 @@ async fn main() -> eyre::Result<()> {
 	let config: ApplicationConfig = figment.extract()?;
 	tracing::debug!(?config, "configuration loaded successfully");
 
-// Make sure applications 		with dynamic accessibility support do expose their AT-SPI2 interfaces.
+	// Make sure applications 		with dynamic accessibility support do expose their AT-SPI2 interfaces.
 	if let Err(e) = atspi_connection::set_session_accessibility(true).await {
 		tracing::debug!("Could not set AT-SPI2 IsEnabled property because: {}", e);
 	}

odilia/src/state.rs

@@ -53,7 +53,11 @@ impl ScreenReaderState {
 		let accessible_history = Mutex::new(CircularQueue::with_capacity(16));
 		let event_history = Mutex::new(CircularQueue::with_capacity(16));
 		let cache = Arc::new(Cache::new(atspi.connection().clone()));
-ssip.send(SSIPRequest::SetRate(ssip_client_async::ClientScope::Current, config.speech().rate)).await?;
+		ssip.send(SSIPRequest::SetRate(
+			ssip_client_async::ClientScope::Current,
+			config.speech().rate,
+		))
+		.await?;
 		Ok(Self {
 			atspi,
 			dbus,