Persist auth information to the iOS keychain (#5460)

* Add initial code hash generation implementation

* Adding auth state to iOS keychain

* Cleanup logging and error handling for initial auth persistence implementation (#5413)

* Cleanup logging and error handling for initial auth persistence implementation

* Update Nullability of error fields and reformat

* Move the error domain and enum into the AuthPersistence file

* Format Mach files

* Externalize handling of nullable error and greedily return on error

* Add initial code hash generation implementation

* Adding auth state to iOS keychain

* Cleanup logging and error handling for initial auth persistence implementation (#5413)

* Cleanup logging and error handling for initial auth persistence implementation

* Update Nullability of error fields and reformat

* Move the error domain and enum into the AuthPersistence file

* Format Mach files

* Externalize handling of nullable error and greedily return on error

* Add unittests for AppDistribution auth persistence

* Split out the keychain calls from control flow and error handling

* Add mocking and tests for auth persistence tests

* Remove debug logging

* Update styling

* Re-add resources to podspec and break out block for readability

Co-authored-by: Jeremy Durham <jeremydurham@google.com>
Co-authored-by: Pranav Rajgopal <pranavrajgopal@google.com>

FirebaseAppDistribution.podspec

@@ -36,8 +36,9 @@ iOS SDK for App Distribution for Firebase.
   }
 
   s.test_spec 'unit' do |unit_tests|
-    unit_tests.source_files = 'FirebaseAppDistribution/Tests/Unit*/*.[mh]'
-    unit_tests.resources = 'FirebaseAppDistribution/Tests/Unit/Resources/*'
+   unit_tests.source_files = 'FirebaseAppDistribution/Tests/Unit*/*.[mh]'
+   unit_tests.resources = 'FirebaseAppDistribution/Tests/Unit/Resources/*'
+   unit_tests.dependency 'OCMock'
   end
 
   # end