Iss #143 - Handle Status event by making PR in hook optional but checked

Resolves #143 (closed)

src/main/java/org/eclipsefoundation/git/eca/api/models/GithubWebhookRequest.java

@@ -11,6 +11,8 @@
  */
 package org.eclipsefoundation.git.eca.api.models;
 
+import javax.annotation.Nullable;
+
 import org.eclipsefoundation.git.eca.dto.GithubWebhookTracking;
 
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
@@ -31,6 +33,7 @@ public abstract class GithubWebhookRequest {
 
     public abstract Repository getRepository();
 
+    @Nullable
     public abstract PullRequest getPullRequest();
 
     /**
@@ -73,7 +76,7 @@ public abstract class GithubWebhookRequest {
 
         public abstract Builder setRepository(Repository repository);
 
-        public abstract Builder setPullRequest(PullRequest pullRequest);
+        public abstract Builder setPullRequest(@Nullable PullRequest pullRequest);
 
         public abstract GithubWebhookRequest build();
     }