As discussed in MongoDB support case 01433340:

When configuring GitHub Actions to manage control plane configurations in public cloud environments (e.g., GCP, Azure, AWS, et cetera), we set up OpenID Connect ("OIDC") to allow the GHA workflows the ability to authenticate with that cloud provider without needing to store credentials as long-lived GitHub secrets (i.e., API keys). Please update and merge to main an official atlas-github-action that allows the option to use of OAuth2 / OIDC (without requiring any API keys).