Duplicate payments were showing up in the discourse ui for users. Actual
transactions in stripe were not being duplicated. This fix ensures that
when parsing the api response we don't append any duplicates. Added a
duplicate entry to the specs to test for this.
I do think there can be some improvements made to this controller
endpoint, but I'd like to save those for a different and larger PR and
just get this fix out first.
* 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
