* Add climate_control gem and test helper
* Replace ENV mods in upgrades test
* Replace ENV mods in registrations test
* Remove ENV references in hostings controller
* Update ENV refs in mailer test
* ActiveStorage cleanup
* Consolidate queue config so appropriate adapter runs in test environment
* Make test environment more explicit
* Centralize self hosting config
* Remove flaky system test
* Implement Synth as an exchange rate provider
* Add assertions to provider interface test
* Assert the correct provider error is raised
* Remove unnecessary parens
