anchor.diff:  `xpack.notification.slack.account.<id>.secure_url`
   
   [float]
  +[[breaking_66_mapping_changes]]
   === Mappings changes
   
   [float]
  
positive.code: // TEST[setup:stackoverflow]
  
  [float]
  === Settings changes
  
  [float]
  
negative.code: 
  The following type parameters are deprecated for the `geo_shape` field type: `tree`,
  `precision`, `tree_levels`, `distance_error_pct`, `points_only`, and `strategy`. They
  will be removed in a future version.
  
  [float]
  [[breaking_66_ml_changes]]
  === Machine learning changes
  
  The get jobs API and get job stats API can retrieve a maximum of 10,000 jobs.
  Likewise, the get datafeeds API and get datafeed stats API can retrieve a
  maximum of 10,000 datafeeds. Prior to version 6.6, there were no limits on the
  results from these APIs. 
  