Comment 3 for bug 1868645

The charm config.yaml says:

    Secret for Horizon to use when securing internal data;
    set this when using multiple dashboard units.

And in the README when talking about HA methods, it says:

    Whichever method has been used to cluster the charm the 'secret'
    option should be set to ensure that the Django secret is
    consistent across all units.

I think that means it doesn't share the secret between units in a multi-unit scenario.