code: func (c *Client) AddResourceApp(providerID, resourceID, appID string) (*ct.Resource, error) {
  	var resource *ct.Resource
  	return resource, c.Put(fmt.Sprintf("/providers/%s/resources/%s/apps/%s", providerID, resourceID, appID), nil, &resource)
  }
docs: // AddResourceApp adds appID to the resource identified by resourceID and returns the resource