As reported [on Meta](https://meta.discourse.org/t/discourse-subscriptions/140818/352?u=justin), moderators could access all of the subscriptions data (plugins/prices/subscribers) and manage them. This should not be the case, so this PR adds a route constraint to 404 moderators from these routes.
Meta topic: https://meta.discourse.org/t/subscriptions-add-pagination-to-admin-subscriptions-view/172500
This adds support for pagination using our `{{load-more}}` component in core. Implementation on the backend was a bit tricky because we don't return all results from Stripe, only those that match local subscriptions stored in the `DiscourseSubscriptions::Subscription` model.
An implementation of refunds from the Admin dashboard. To refund, go to Plugins > Subscriptions > Subscriptions then click the `Cancel` button. You'll be presented with a modal. If you wish to refund only the most recent payment, check the box.
This only implements refunds for Subscriptions, not One Time Payments. One Time Payments will still need to be handled manually at this time.
* REFACTOR: Use api to add subscribe link
* FIX: I18n subscribe link
* REFACTOR: Use models to store some data
This enables the plugin to show only subscription information which was
generated on Discourse. Subscription data storage is limited to the
external identifiers Stripe generates so we can interact with the API.
* DEV: Test/linting fixes/rake task
