Issue #3320760: Add encryption option to backup schedule

config/schema/backup_migrate.schema.yml

@@ -37,6 +37,12 @@ backup_migrate.backup_migrate_schedule.*:
     keep:
       type: integer
       label: 'Backups to keep'
+    encrypt:
+      type: boolean
+      label: 'Encrypt'
+    encrypt_password:
+      type: string
+      label: 'Encryption Password'
     period:
       type: integer
       label: 'Frequency'