Add trait requirements for DeviceBackend

src/devices/mod.rs

@@ -137,7 +137,7 @@ impl From<u8> for AttributeValue {
     }
 }
 
-pub trait DeviceBackend {
+pub trait DeviceBackend: Send + Sync {
     fn build_query(&self) -> CommandRequest;
     fn process_message(&mut self, msg: &[u8]);
     fn attributes(&self) -> &HashMap<&'static str, AttributeValue>;