Ensure cloud instance snapshots are encrypted through Google Compute Snapshot

Google Compute instance VMs that have disk encryption enabled with customer supplied keys must also have the snapshots encrypted with a customer supplied key. For more on encryption of Compute Engine disks and snapshots, see the GCP documentation.
References:
https://cloud.google.com/compute/docs/disks/customer-supplied-encryption#create_snapshot

The encryption configuration can only be configured during the process of provisioning the snapshot.

In GCP Console -

1. Open the Snapshot page.
2. Select create snapshot, Configure Encryption type to Required type.
3. Click Create.

In Terraform -

1. In the google_compute_snapshot resource, ensure that snapshot_encryption_key block attribute is added with valid KMS Key details like kms_key_self_link, kms_key_service_account and raw_key.

References:
https://registry.terraform.io/providers/hashicorp/google/4.50.0/docs/resources/compute_snapshot#nested_snapshot_encryption_key
https://cloud.google.com/compute/docs/disks/customer-supplied-encryption