docs: function sendSenderAction (recipient, sender_action) {
    return new Promise (async (resolve, reject) => {
      if (!sender_action) {
        reject('sender_action required');      
      }
  
      let payload = {
        'sender_action': sender_action
      };
  
      try {
        let response = await this.callSendApi(recipient, payload);  
        resolve(response);
      } catch (e) {
        reject(e);
      }
    });
  }