Values:
ENCRYPTION_TYPE_UNSPECIFIED (0):
Unspecified. Do not use.
USE_CONFIG_DEFAULT_OR_BACKUP_ENCRYPTION (1):
This is the default option when
encryption_config][google.spanner.admin.database.v1.RestoreDatabaseEncryptionConfig]
is not specified.
GOOGLE_DEFAULT_ENCRYPTION (2):
Use Google default encryption.
CUSTOMER_MANAGED_ENCRYPTION (3):
Use customer managed encryption. If specified,
kms_key_name must must contain a valid Cloud KMS key.