As a User when I pin or unpin a File I expect my preference to be saved to my account.

1) myPins array for the User must be updated via a PUT request from list.jsx on click of the bookmark icon. In order for that to happen, currentUser must be passed down to the List component.
2) the string "currentUserId" must be replaced in list.jsx with the actual user._id once that User object is passed down and available to the component