Authenticated users with an existing subscription are able to purchase a new plan (instead of changing the plan) when single-plan mode is enabled.

I wonder if we should add a message ($this->messenger()->setMessage()) and either display it on the page that you are redirected too, or instead of automatically displaying a redirect display a link to the change subscription page instead? I feel like it could be kind of confusing if you click a link that says "Signup" and you end up on a "Edit your existing plan" page without any other context. Thoughts?

Otherwise, yeah I agree this is a bug and should get fixed.

I added a test that proves this new logic is working. And a message that gets displayed on the page that the user gets redirected too. If you think this is a good approach we can merge this in. Otherwise I'm open to other ideas about how to best guide users.

Yea, I think the message is good.

Thanks!