Add missing max_boost parameter to function score query

Author: gmarz

src/Nest/DSL/Query/FunctionScoreQueryDescriptor.cs

@@ -27,6 +27,9 @@ public interface IFunctionScoreQuery : IQuery
 		[JsonConverter(typeof (StringEnumConverter))]
 		FunctionBoostMode? BoostMode { get; set; }
 
+		[JsonProperty("max_boost")]
+		float? MaxBoost { get; set; }
+
 		[JsonProperty(PropertyName = "random_score")]
 		IRandomScoreFunction RandomScore { get; set; }
 
@@ -46,6 +49,7 @@ protected override void WrapInContainer(IQueryContainer container)
 		public IQueryContainer Query { get; set; }
 		public FunctionScoreMode? ScoreMode { get; set; }
 		public FunctionBoostMode? BoostMode { get; set; }
+		public float? MaxBoost { get; set; }
 		public IRandomScoreFunction RandomScore { get; set; }
 		public IScriptFilter ScriptScore { get; set; }
 	}
@@ -60,6 +64,8 @@ public class FunctionScoreQueryDescriptor<T> : IFunctionScoreQuery where T : cla
 
 		FunctionBoostMode? IFunctionScoreQuery.BoostMode { get; set; }
 
+		float? IFunctionScoreQuery.MaxBoost { get; set; }
+
 		IRandomScoreFunction IFunctionScoreQuery.RandomScore { get; set; }
 
 		IScriptFilter IFunctionScoreQuery.ScriptScore { get; set; }
@@ -110,6 +116,12 @@ public FunctionScoreQueryDescriptor<T> BoostMode(FunctionBoostMode mode)
 			return this;
 		}
 
+		public FunctionScoreQueryDescriptor<T> MaxBoost(float maxBoost)
+		{
+			((IFunctionScoreQuery)this).MaxBoost = maxBoost;
+			return this;
+		}
+
 		public FunctionScoreQueryDescriptor<T> RandomScore(int? seed = null)
 		{
 			((IFunctionScoreQuery)this).RandomScore = new RandomScoreFunction();

src/Tests/Nest.Tests.Unit/QueryParsers/Queries/FunctionScoreQueryTests.cs

@@ -15,6 +15,7 @@ public void FunctionScore_Deserializes()
 				f=>f.FunctionScore,
 				f=>f.FunctionScore(fq=>fq
 					.BoostMode(FunctionBoostMode.Average)
+					.MaxBoost(0.95f)
 					.Functions(
 						ff => ff.Gauss(x => x.StartedOn, d => d.Scale("42w")),
 						ff => ff.Linear(x => x.FloatValue, d => d.Scale("0.3")),
@@ -33,6 +34,7 @@ public void FunctionScore_Deserializes()
 				);
 
 			q.BoostMode.Should().Be(FunctionBoostMode.Average);
+			q.MaxBoost.Should().Be(0.95f);
 			q.RandomScore.Should().NotBeNull();
 			q.RandomScore.Seed.Should().Be(1337);
 			q.ScoreMode.Should().Be(FunctionScoreMode.First);