Checklist

• I've run bundle exec rspec from the root directory to see all new and existing tests pass
• I've followed the fastlane code style and run bundle exec rubocop -a to ensure the code style is valid
• I see several green ci/circleci builds in the "All checks have passed" section of my PR (connect CircleCI to GitHub if not)
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.
• I've added or updated relevant unit tests.

Motivation and Context

We use supply method to upload our app bundle (Android) to Play Store. Recently we are migrating our service account key usage to Workload Identity Federation (WIF) in order to enhance the security.

Description

Added validation to check whether it's an external_account or service_account to fix error missing client_email caused by https://github.com/googleapis/google-auth-library-ruby/blob/main/lib/googleauth/json_key_reader.rb#L24 when using Workload Identity Federation

• service_account –> Google::Auth::ServiceAccountCredentials
• external_account –> Google::Auth::ExternalAccount::Credentials

Testing Steps

Successfully validate the credential using the credential config from WIF