Celery 6.0 will require a separate setting to enable retry on startup

[MoralCode]

Very much not urgent and not causing issues, but figured i would document this warning that I got when running the dev environment in case there are future plans to upgrade the Celery dependency

The broker_connection_retry configuration setting will no longer determine
whether broker connection retries are made during startup in Celery 6.0 and above.
If you wish to retain the existing behavior for retrying connections on startup,
you should set broker_connection_retry_on_startup to True.