Values:
ENCRYPTION_TYPE_UNSPECIFIED (0):
Unspecified. Do not use.
USE_CONFIG_DEFAULT_OR_BACKUP_ENCRYPTION (1):
This is the default option for
CopyBackup][google.spanner.admin.database.v1.DatabaseAdmin.CopyBackup]
when
encryption_config][google.spanner.admin.database.v1.CopyBackupEncryptionConfig]
is not specified. For example, if the source backup is using
Customer_Managed_Encryption, the backup will be using
the same Cloud KMS key as the source backup.
GOOGLE_DEFAULT_ENCRYPTION (2):
Use Google default encryption.
CUSTOMER_MANAGED_ENCRYPTION (3):
Use customer managed encryption. If specified,
kms_key_name must contain a valid Cloud KMS key.
