All dialogs have hardcoded label keys:

    <sv:property sv:name="label" sv:type="String">
      <sv:value>dialog.forumAdd.label</sv:value>
    </sv:property>

1. Remove hardcoded labels from bootstrap files.
2. We should use info.magnolia.i18nsystem.setup.RemoveHardcodedI18nPropertiesFromDialogsTask to remove hardcoded label keys on update.
3. Translation of the dialogs commes from obsolete /forum/src/main/resources/info/magnolia/module/forum/messages_*.properties files -> these should be moved to /forum/src/main/resources/mgnl-i18n so there will be no need to specify key labels.