package:googleapis_auth v2.1.0

• AuthClientSigningExtension: Added sign() which accepts an optional
  serviceAccountCredentials argument, and getServiceAccountEmail().
• ServiceAccountCredentials
  • Added parsing for projectId and universeDomain properties.
  • Added sign() method for RSA-SHA256 signing.
• Added signBlob() function for signing via IAM Credentials API.
• MetadataServerAuthorizationFlow
  • Now uses getMetadataValue (caching) and fetchMetadataValue
    (non-caching) from package:google_cloud.
  • Added refresh support to run().
• Added clientViaServiceAccountImpersonation() function and
  ImpersonatedAuthClient class for service account impersonation via IAM
  Credentials API.
• Export RSAPrivateKey which is exposed by ServiceAccountCredentials.
• Require google_cloud: ^0.3.0.
• Require meta: ^1.15.0.
• Require sdk: ^3.9.0.
• Drop unneeded args dependency.