I haven't implemented the unregistration. Until now it was not necessary, because there are not so many regIds to unregister. So I send me an email (through a rule) with the deactivated regIds and delete them manual with a sql-statement into the database. In some weeks I will find the way to do it also automatic via android and Drupal. May be some other readers of this article tried it and could leave a comment here. If not, I will post the solution after finding it.
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