text: export const ADD_USER = 'add_user';
  export const DELETE_USER = 'delete_user';
  export const UNDO = 'undo';
  export const REDO = 'redo';
  
  export const addUser = (user) => {
      return {
          type: ADD_USER,
          user
      }
  }
  
  export const deleteUser = (user) => {
      return {
          type: DELETE_USER,
          user
      }
  }
  
  export const undo = () => ({ type: UNDO });
  
  export const redo = () => ({ type: REDO });