What action should you take to resolve the "403 Forbidden" error when writing to a Cloud Storage bucket owned by another project?

To resolve the "403 Forbidden" error when writing to a Cloud Storage bucket owned by another project, granting the service account the roles/storage.objectCreator role for the bucket is the most effective action. This role specifically allows the assigned entity (in this case, the service account) to create objects within the specified Cloud Storage bucket.

When an application tries to write data into a bucket it does not own, it must have the correct permissions set on that bucket. The roles/storage.objectCreator role provides necessary permissions to allow the service account to perform write operations. By granting this permission to the service account, you enable the necessary actions that allow data to be written successfully without encountering access denial errors.

While the other options might seem like potential solutions, they do not directly address the core issue of authorizing the service account to perform write operations within the target bucket. Assigning the roles/storage.objectCreator role directly aligns with resolving the permissions required for writing data, leading to successful interactions with the Cloud Storage bucket.