UserCreationListener e-mail spam during JIRA migration

In jira-ondemand-project/jira-ondemand-plugins/jira-ondemand-theme-plugin/src/main/java/com/atlassian/studio/jira/haup/UserCreationListener.java the following code currently exists:

        for (com.atlassian.crowd.embedded.api.User user : userUtil.getAllUsersInGroups(permissionManager.getGroupsWithPermission(Permissions.ADMINISTER)))
        {   
            Email email = new Email(user.getEmailAddress());
            email.setSubject(i18n.getText("studio.jira.email.grant.failure.conflictnotification.subject"));
            email.setMimeType("text/html");
            email.setBody(emailBody);
            mailQueue.addItem(new SingleMailQueueItem(email));
        }   

As everyone on jira-dev (and many people outside of jira-dev) noticed when 2 migrations I attempted failed to upgrade over 100 of the users, spamming one e-mail per failed user is really unacceptable. This needs to be changed to coalesce multiple failures with the same target address.

It looks like onUserCreation also tries to exempt UserCreatedFromDirectorySynchronisationEvent messages, so perhaps doing something similar to ignore failures during data migration would be a simpler option.