Scenario: Your organization has two Google Cloud projects: project A and project B. In project A, there is a Pub/Sub topic that receives data from confidential sources. You need to ensure that only resources in project A can access the data in this topic. You want to prevent project B, or any future project, from accessing the topic in project A. Question: How can you ensure that only resources in project A can access the Pub/Sub topic, while preventing access from project B or other future projects?