[google-auth-library-java] Serialization Issues: Auth Library transient keyword usage #12580

There have a few reports of the transient keyword resulting in Null Pointer Exceptions (NPE) when serializing credentials.

This ticket is to track the reports and see how much this is impacting users. We may need to investigate the usage of serializing the Credentials and certain transient fields.

Issues:

• Flink app hosted in AWS trying to publish to GCP and throwing NPE at com.google.auth.oauth2.InternalAwsSecurityCredentialsSupplier.retrieveResource google-auth-library-java#1538
• ExternalAccountCredentials serialization is broken google-auth-library-java#1347
• b/416096444
• [google-auth-library-java] external_account (AWS) Credentials NPE after Java deserialization: transient HttpTransportFactory not restored on refresh #14050

Artifact/ Proof of the Issue(s):

• chore: demonstration of null calendar after reserialization of ImpersonatedCredentials google-auth-library-java#1772 - Calendar is transient and leads to a NPE when serializing