If public-url is undefined, charm "works" (green/pod alive) but doesn't do anything useful

[ca-scribner]

If deployed and related to the appropriate charms but not set with a public-url, OIDC-gatekeeper will show:

• Active in juju
• pod running
• pod logs show repeated messages of time="2022-02-11T18:18:01Z" level=error msg="OIDC provider setup failed, retrying in 10 seconds: Get /dex/.well-known/openid-configuration: unsupported protocol scheme \"\""
  This will also result in a blank screen if trying to browse to the ingress IP because the dex+oidc handling of the login is broken. No useful messages are provided to the user to identify what is wrong.

I think at minimum we need better messaging about this to nudge users in the right direction. But I also think (? haven't thought it through deeply) the oidc-gatekeeper charm shouldn't be live at all if it has no public-url. With public-url="" it just tries to do the auth flow with a non-sensical IP address. A deeper look into this might show we're doing it right but it seems worth a look. Either way, for our purposes I don't think juju status should show green if this is the case as no users can log in

[ca-scribner]

As pointed out by @grobbie, rather than setting public-url directly should we get the info we need from a relation with dex-auth?

[orfeas-k]

Closed by #108