* Read and import the secrets from ClassicAppAccounts.
* Record snapshots.
* Add some documentation, tidy up tests and fix the dismissal of the backup instructions.
* Workaround flakey tests (the fulfilments weren't always firing).
* Allow a custom Classic App deep link URL to be configured.
- Create an app.yml with the base app variant.
- Override app.yml contents on Nightly/PR builds.
- Add AppHooks mechanism.
- Add Enterprise submodule.
- Conditionally import Enterprise/fastlane/Fastfile if available.