Storage: Implement Bucket-Level IAM Policy Management

[stephenplusplus]

• getIamPolicy
• setIamPolicy
• testIamPolicy

[bjwatson]

This is not release blocking. The API team has pushed out bucket-level IAM until later.

[stephenplusplus]

Marking as blocked as we're still waiting on whitelisting.

[lukesneeringer]

Summoning @elibixby. Not sure if you are the right person, but I think you might be -- can we get whitelisted, pretty please? :-)

[elibixby]

Nope unfortunately, try pinging yarbrough@ ... You might also want to get notified whitelisted for the new GCS Change Notifications (which work via Pub/Sub) while you're at it.