code: def default_receiver
        cep = collection_event_parameters
        cltr = cep.user if cep
        return cltr if cltr
        cp = collection_protocol || return
        rcv = cp.coordinators.first
        return rcv if rcv or cp.fetched?
        # Try to fetch the CP coordinator 
        return cp.coordinators.first if cp.find
        # CP does not exist; add the CP defaults and retry
        cp.add_defaults
        cp.coordinators.first
      end
docs: Returns the collection protocol coordinator. Fetches the CP if necessary and possible.
   Adds defaults to the CP if necessary, which sets a default coordinator if possible.
  
   @return [CaTissue::User] the default receiver