BLE: Add "service change attribute", advertise service

BLE can only fit 251 bytes of payload in notifications which isn't nearly enough for a raw V2X message.
So only publish a notification which message was received and let the client
poll the content from the characteristic (since reads can get data in fragments)

src/ble.rs

@@ -193,10 +193,10 @@ pub async fn run(
         "Starting advertising and GATT service for {}",
         features.join(",")
     );
-    let server = Server::new_with_config(PeripheralConfig {
+    let server = Server::new_with_config(GapConfig::Peripheral(PeripheralConfig {
         name: &name,
-        appearance: &appearance::UNKNOWN, // maybe appearance::outdoor_sports_activity::LOCATION_AND_NAVIGATION_DISPLAY ?
+        appearance: &appearance::UNKNOWN,
-    })
+    }))
     .unwrap();
 
     let _ = embassy_futures::join::join(ble_task(runner), async {