Fix #1867 objects can now be serialized in register percolater metadata

Author: gmarz

src/Nest/Search/Percolator/RegisterPercolator/RegisterPercolatorJsonConverter.cs

@@ -49,7 +49,14 @@ public override void WriteJson(JsonWriter writer, object value, JsonSerializer s
 				foreach(var kv in request.Metadata)
 				{
 					writer.WritePropertyName(kv.Key);
-					writer.WriteValue(kv.Value);
+					if (kv.Value.GetType().IsValueType)
+					{
+						writer.WriteValue(kv.Value);
+					}
+					else
+					{
+						serializer.Serialize(writer, kv.Value);
+					}
 				}
 			}
 

src/Tests/Search/Percolator/RegisterPercolator/RegisterPercolatorApiTests.cs

@@ -47,7 +47,8 @@ protected override LazyResponses ClientUsage() => Calls(
 				match = new { name = new { query = "nest" } }
 			},
 			language = "c#",
-			commits = 5000
+			commits = 5000,
+			project = Project.Instance
 		};
 
 		protected override void ExpectResponse(IRegisterPercolatorResponse response)
@@ -70,6 +71,7 @@ protected override void ExpectResponse(IRegisterPercolatorResponse response)
 			.Metadata(md => md
 				.Add("language", "c#")
 				.Add("commits", 5000)
+				.Add("project", Project.Instance)
 			);
 
 		protected override RegisterPercolatorRequest Initializer => new RegisterPercolatorRequest(this.CallIsolatedValue + "-index", this.CallIsolatedValue)
@@ -82,7 +84,8 @@ protected override void ExpectResponse(IRegisterPercolatorResponse response)
 			Metadata = new Dictionary<string, object>
 			{
 				{ "language", "c#" },
-				{ "commits", 5000 }
+				{ "commits", 5000 },
+				{ "project", Project.Instance }
 			}
 		};
 	}