def add_action(content_uid, verb, userids=None, completed=False):
    """
        Add the given action for the given content to the given users, or all
        users. If completed is True then this is an action that has occurred
        (for example "Liking" content) rather than an action that needs to be
        take in the future

        :param content_uid: The UID of the content
        :type content_uid: str
        :param verb: The action to take
        :type verb: str
        :param userids: The userids to add the action to or None for all users
        :type userids: str or list or None
        :param completed: Whether this is a pre-completed action
        :type completed: bool
        """
