Add annotations_enabled to model config (#4919)

Relates: elastic/elasticsearch#57539

src/Nest/XPack/MachineLearning/Job/Config/ModelPlotConfig.cs

@@ -23,6 +23,15 @@ public interface IModelPlotConfig : IModelPlotConfigEnabled
 		/// </remarks>
 		[DataMember(Name ="terms")]
 		Fields Terms { get; set; }
+
+		/// <summary>
+		/// If <c>true</c>, enables calculation and storage of the model change annotations
+		/// for each entity that is being analyzed. By default, this is not enabled.
+		/// <para />
+		/// Valid in Elasticsearch 7.9.0+
+		/// </summary>
+		[DataMember(Name = "annotations_enabled")]
+		bool? AnnotationsEnabled { get; set; }
 	}
 
 	/// <inheritdoc />
@@ -33,23 +42,31 @@ public class ModelPlotConfig : IModelPlotConfig
 
 		/// <inheritdoc />
 		public Fields Terms { get; set; }
+
+		/// <inheritdoc />
+		public bool? AnnotationsEnabled { get; set; }
 	}
 
 	/// <inheritdoc />
 	public class ModelPlotConfigDescriptor<T> : DescriptorBase<ModelPlotConfigDescriptor<T>, IModelPlotConfig>, IModelPlotConfig where T : class
 	{
 		bool? IModelPlotConfigEnabled.Enabled { get; set; }
 		Fields IModelPlotConfig.Terms { get; set; }
+		bool? IModelPlotConfig.AnnotationsEnabled { get; set; }
 
-		/// <inheritdoc />
+		/// <inheritdoc cref="IModelPlotConfigEnabled.Enabled" />
 		public ModelPlotConfigDescriptor<T> Enabled(bool? enabled = true) => Assign(enabled, (a, v) => a.Enabled = v);
 
-		/// <inheritdoc />
+		/// <inheritdoc cref="IModelPlotConfig.Terms" />
 		public ModelPlotConfigDescriptor<T> Terms(Func<FieldsDescriptor<T>, IPromise<Fields>> fields) =>
 			Assign(fields, (a, v) => a.Terms = v?.Invoke(new FieldsDescriptor<T>())?.Value);
 
-		/// <inheritdoc />
+		/// <inheritdoc cref="IModelPlotConfig.Terms" />
 		public ModelPlotConfigDescriptor<T> Terms(Fields fields) => Assign(fields, (a, v) => a.Terms = v);
+
+		/// <inheritdoc cref="IModelPlotConfig.AnnotationsEnabled" />
+		public ModelPlotConfigDescriptor<T> AnnotationsEnabled(bool? enabled = true) =>
+			Assign(enabled, (a, v) => a.AnnotationsEnabled = v);
 	}
 
 	/// <summary>