anchor.diff:  PUT /_snapshot/my_backup/snapshot_1
   {
     "indices": "index_1,index_2",
  -  "ignore_unavailable": "true",
  +  "ignore_unavailable": true,
     "include_global_state": false
   }
   -----------------------------------
  
positive.code: POST /_snapshot/my_backup/snapshot_1/_restore
  {
    "indices": "index_1,index_2",
    "ignore_unavailable": "true",
    "include_global_state": true,
    "rename_pattern": "index_(.+)",
    "rename_replacement": "restored_index_$1"
  
negative.code:   "my_backup": {
      "type": "fs",
      "settings": {
        "compress": true,
        "location": "/mount/backups/my_backup"
      }
    }
  