The import script has a prompt asking if this is a "procourse" import or
not, but the logic for handling the answer is backwards and will
incorrectly set the `procourse_import` flag to `true`.
This commit also fixes a minor typo.
* 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