Add comments to remove classes

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/job/retention/ExpiredForecastsRemover.java

@@ -45,6 +45,10 @@
  * Removes up to {@link #MAX_FORECASTS} forecasts (stats + forecasts docs) that have expired.
  * A forecast is deleted if its expiration timestamp is earlier
  * than the start of the current day (local time-zone).
+ *
+ * This is expected to be used by actions requiring admin rights. Thus,
+ * it is also expected that the provided client will be a client with the
+ * ML origin so that permissions to manage ML indices are met.
  */
 public class ExpiredForecastsRemover implements MlDataRemover {
 

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/job/retention/ExpiredModelSnapshotsRemover.java

@@ -34,6 +34,10 @@
  * of their respective job with the exception of the currently used snapshot.
  * A snapshot is deleted if its timestamp is earlier than the start of the
  * current day (local time-zone) minus the retention period.
+ *
+ * This is expected to be used by actions requiring admin rights. Thus,
+ * it is also expected that the provided client will be a client with the
+ * ML origin so that permissions to manage ML indices are met.
  */
 public class ExpiredModelSnapshotsRemover extends AbstractExpiredJobDataRemover {
 

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/job/retention/ExpiredResultsRemover.java

@@ -38,6 +38,10 @@
  * of their respective job. A result is deleted if its timestamp is earlier
  * than the start of the current day (local time-zone) minus the retention
  * period.
+ *
+ * This is expected to be used by actions requiring admin rights. Thus,
+ * it is also expected that the provided client will be a client with the
+ * ML origin so that permissions to manage ML indices are met.
  */
 public class ExpiredResultsRemover extends AbstractExpiredJobDataRemover {