Handle the Unassigned assignee set after real user was set

src/main/java/org/hibernate/infra/replicate/jira/service/jira/handler/JiraIssueAbstractEventHandler.java

@@ -121,6 +121,11 @@ protected JiraIssue issueToCreate(JiraIssue sourceIssue) {
 		if (sourceIssue.fields.assignee != null) {
 			destinationIssue.fields.assignee = user(sourceIssue.fields.assignee).map(this::toUser)
 					.orElseGet(context::notMappedAssignee);
+		} else {
+			// Because not sending an assignee just does not update it:
+			// See also
+			// https://confluence.atlassian.com/jirakb/how-to-set-assignee-to-unassigned-via-rest-api-in-jira-744721880.html
+			destinationIssue.fields.assignee = JiraUser.unassigned(context.projectGroup().users().mappedPropertyName());
 		}
 
 		return destinationIssue;

src/main/java/org/hibernate/infra/replicate/jira/service/jira/model/rest/JiraUser.java

@@ -21,4 +21,8 @@ public JiraUser(String propertyName, String value) {
 			properties().put(propertyName, value);
 		}
 	}
+
+	public static JiraUser unassigned(String propertyName) {
+		return new JiraUser(propertyName, null);
+	}
 }

src/main/resources/application.properties

@@ -2,6 +2,9 @@
 #
 # So that we have /api prefix in all our REST paths:
 quarkus.rest.path=/api
+# Enable access logs, in particular to see if web hook is triggered:
+quarkus.http.access-log.enabled=true
+quarkus.log.category."io.quarkus.http.access-log".level=INFO
 # Management endpoints:
 quarkus.management.enabled=true
 quarkus.management.auth.basic=true