Improves the subscription flow for anonymous users by making the routes available, and showing a login button. Clicking login from this page will save a `destination_url` cookie so that when logging in they're redirected back to the subscription page they were at.
Building off the foundation of using the Prices API, this PR adds the ability to create a one-time purchase plan for any product, which then can add a user to the specified plan group.
Some things to be aware of:
One-time purchases cannot have trials.
One-time purchases use the Invoice API instead of Subscriptions. Invoices are created then charged immediately.
Users should receive emails for these invoices directly from Stripe just like subscriptions.
- Replace deprecated methods on client
- Fix broken dropdowns due to select kit 2 upgrade
- Graceful error handling when Stripe keys are not configured but plugin enabled