[DPE-3361] chore: sort bootstrap_servers to avoid repeated client-rel…

…ation-changed (#174)

src/core/cluster.py

@@ -135,7 +135,7 @@ def bootstrap_server(self) -> list[str]:
         if not self.peer_relation:
             return []
 
-        return [f"{host}:{self.port}" for host in self.unit_hosts]
+        return sorted([f"{host}:{self.port}" for host in self.unit_hosts])
 
     @property
     def log_dirs(self) -> str: