code: public PanelUser updateJoinType(PanelUser panelUser, PanelUserJoinType joinType, User modifier) {
      panelUser.setJoinType(joinType);
      panelUser.setLastModified(new Date());
      panelUser.setLastModifier(modifier);
      
      return persist(panelUser);
    }
docs: Updates panel user's join type
  
  @param panelUser panel user
  @param joinType new join type
  @param modifier modifier
  @return updated user