Billing (#1269)

* Change env SELF_HOSTING_ENABLED to SELF_HOSTED

* Initial Stripe implementation

* Fix portal link

* Use webhook signatures

* Migrated to new Stripe gem conventions

Also updated resource routing

* Added faraday-multipart gem to resolve middleware notice

* Merge fix

* Merge fix

* Temporary upgrade prompt for early access

* Lint fix

* i18n fixes

* Remove catch-all rescue

* Update .env.example

test/controllers/subscriptions_controller_test.rb

@@ -0,0 +1,7 @@
+require "test_helper"
+
+class SubscriptionsControllerTest < ActionDispatch::IntegrationTest
+  # test "the truth" do
+  #   assert true
+  # end
+end