Added ClosedBy and ClosedAt property to issues and merge-requests (#37)

* Added ClosedBy and ClosedAt property to issues and merge-requests

* Fixed build errors

Author: dnagl

src/GitLabApiClient/Models/Issues/Responses/Issue.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using GitLabApiClient.Models.Milestones.Responses;
 using Newtonsoft.Json;
@@ -33,6 +34,12 @@ public sealed class Issue : ModifiableObject
         [JsonProperty("milestone")]
         public Milestone Milestone { get; set; }
 
+        [JsonProperty("closed_at")]
+        public DateTime? ClosedAt { get; set; }
+
+        [JsonProperty("closed_by")]
+        public string ClosedBy { get; set; }
+
         [JsonProperty("title")]
         public string Title { get; set; }
 

src/GitLabApiClient/Models/MergeRequests/Responses/MergeRequest.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using GitLabApiClient.Models.Milestones.Responses;
 using Newtonsoft.Json;
@@ -57,6 +58,12 @@ public sealed class MergeRequest : ModifiableObject
         [JsonProperty("source_project_id")]
         public int SourceProjectId { get; set; }
 
+        [JsonProperty("closed_at")]
+        public DateTime? ClosedAt { get; set; }
+
+        [JsonProperty("closed_by")]
+        public string ClosedBy { get; set; }
+
         [JsonProperty("target_branch")]
         public string TargetBranch { get; set; }