Add headPipeline to MergeRequest (gitlab4j#890)

Co-authored-by: Jérémie Bresson <dev@jmini.fr>

Author: vimsucks

src/main/java/org/gitlab4j/api/models/MergeRequest.java

@@ -54,6 +54,7 @@ public class MergeRequest {
     private String mergeError;
     private Milestone milestone;
     private Pipeline pipeline;
+    private Pipeline headPipeline;
     private Long projectId;
     private String sha;
     private Boolean shouldRemoveSourceBranch;
@@ -374,6 +375,14 @@ public void setPipeline(Pipeline pipeline) {
         this.pipeline = pipeline;
     }
 
+    public Pipeline getHeadPipeline() {
+        return headPipeline;
+    }
+
+    public void setHeadPipeline(Pipeline headPipeline) {
+        this.headPipeline = headPipeline;
+    }
+
     public Long getProjectId() {
         return projectId;
     }

src/main/java/org/gitlab4j/api/models/Pipeline.java

@@ -8,6 +8,7 @@
 public class Pipeline {
 
     private Long id;
+    private Long projectId;
     private PipelineStatus status;
     private String ref;
     private String sha;
@@ -34,6 +35,14 @@ public void setId(Long id) {
         this.id = id;
     }
 
+    public Long getProjectId() {
+        return projectId;
+    }
+
+    public void setProjectId(Long projectId) {
+        this.projectId = projectId;
+    }
+
     public PipelineStatus getStatus() {
         return status;
     }

src/test/resources/org/gitlab4j/api/merge-request.json

@@ -74,5 +74,34 @@
     "blocking_discussions_resolved": true,
     "diverged_commits_count": 2,
     "latest_build_started_at": "2018-09-07T07:27:38.472Z",
-    "latest_build_finished_at": "2018-09-07T08:07:06.012Z"
+    "latest_build_finished_at": "2018-09-07T08:07:06.012Z",
+    "head_pipeline": {
+        "id": 1,
+        "project_id": 3,
+        "sha": "2be7ddb704c7b6b83732fdd5b9f09d5a397b5f8f",
+        "ref": "test1",
+        "status": "pending",
+        "created_at": "2018-09-07T07:27:38.472Z",
+        "updated_at": "2018-09-07T07:27:38.472Z",
+        "web_url": "https://www.google.com/",
+        "before_sha": "0000000000000000000000000000000000000000",
+        "tag": false,
+        "user": {
+            "id":1,
+            "username": "admin",
+            "state": "active",
+            "email":"admin@local.host",
+            "name":"Administrator"
+        },
+        "detailed_status": {
+            "icon": "status_pending",
+            "text": "pending",
+            "label": "pending",
+            "group": "pending",
+            "tooltip": "pending",
+            "has_details": true,
+            "details_path": "/my-group/my-project/-/pipelines/1",
+            "favicon": "https://www.google.com/"
+        }
+    }
 }