Support Application Default Credentials or Workload Identity when running in GCP

[colinman]

/kind feature

Describe the solution you'd like

Exporting service account credentials and storing in K8S secret store introduces an unnecessary secret and potential point of compromise if the cluster API provider is running inside GCP.

In this case, the provider should first look for Application Default Credentials or use workload identity before requiring service account credential keys.

[fejta-bot]

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[detiber]

/lifecycle frozen
/help

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[prksu]

/assign

[itspngu]

This would be really useful, at least if initially Application Default Credentials were supported - use of Workload Identity from within a Management cluster running on GKE could be built on top of that. @prksu are you currently still working on this? I'd like to see if I can contribute to this if needed.