Track subscription add/removes

src/subscription.rs

@@ -83,6 +83,9 @@ impl Subscription {
     pub fn parse(json: &str) -> Result<Subscription> {
         serde_json::from_str(json).map_err(|e| Error::JsonParseFailed(e))
     }
+    pub fn get_id(&self) -> String {
+        self.id.clone()
+    }
 }
 
 #[cfg(test)]