public static Result vote(String ownerName, String projectName, Long issueNumber) {
Project project = Project.findByOwnerAndProjectName(ownerName, projectName);
Issue issue = Issue.findByNumber(project, issueNumber);
issue.addVoter(UserApp.currentUser());
Call call = routes.IssueApp.issue(ownerName, projectName, issueNumber);
return redirect(call);
}