MountConfigAuthGcpSandboxesSandboxGcpMountWorkloadIdentityAuthConfig()WorkloadIdentityProvider federates an OIDC token LangSmith signs for this
workspace through Workload Identity Federation instead of a service account key:
//iam.googleapis.com/projects/
ServiceAccountEmail is the service account to impersonate with the federated token. Omit it to use the federated principal directly. Only valid with workload_identity_provider.
SubjectScope picks the token subject the provider trusts: "workspace" (the
default) or "tag: