fix: add proxy container wait strategy to prevent flaky tests

Author: mridang

test/test_transport_options.py

@@ -6,6 +6,7 @@
 
 from testcontainers.core.container import DockerContainer
 from testcontainers.core.network import Network
+from testcontainers.core.wait_strategies import PortWaitStrategy
 from testcontainers.core.waiting_utils import wait_container_is_ready
 
 from zitadel_client.transport_options import TransportOptions
@@ -61,6 +62,7 @@ def setup_class(cls) -> None:
             .with_network(cls.network)
             .with_exposed_ports(3128)
             .with_volume_mapping(squid_conf, "/etc/squid/squid.conf", mode="ro")
+            .waiting_for(PortWaitStrategy(3128))
         )
         cls.proxy.start()