* Check if reverse client ID is registered as a custom URL scheme before setting it as the callback scheme.
* Fix existing tests.
* Add tests.
* Update changelog.
* Add Auth emulator support for IdentityToolkit requests.
* Formatting.
* Store the emulator URL in FIRAuthRequestConfiguration.
* Add support for emulating the web widget and SecureTokenService.
* Explicitly cast NSInteger to long to fix warning.
* Add unit tests.
* Fix copyright notice text.
* Remove useEmulator from the public API and disable app verification features when using the emulator.
* Fix test.
* Revert changes to FIRPhoneAuthProvider -- these are unnecessary for emulator support.
* Fix test.
* Fix test.
* Address review comments.
* Use GOOGLE_APP_ID instead of CLIENT_ID if CLIENT_ID is unavailable for generic IDP and phone auth flows.
* Add a prefix to the custom URL scheme when using the Firebase app ID.
* Add tests for FIROAuthProvider.
* Add tests for FIRPhoneAuthProvider.
* Change query param from firebaseAppId to appId.
* Fix tests.
* Address review comments.
* Add changelog entry.