Acceptance Criteria

• A user looking at an article is able to add an article to a collection by clicking a button. See eventlogging requirements from: https://trello.com/c/G4J6JSyF/4-a-user-is-able-to-add-an-article-to-a-new-collection
• Upon clicking the button, existing collection1, existing collection2... are among the options shown.
• If the user is logged in: Upon selecting existing collection, a temporary notification of success is shown [optional?:and a link to edit/share the collection is included in that notification]
• If the user is not logged in: see "https://trello.com/c/CdD1LGxi/2-a-loggedout-user-attempting-to-add-to-a-collection-is-referred-to-login-or-create-account-so-that-they-can-login"
• If there are more than X collections in the list __ treatment comes into play
• upon hitting "back" icon to return to article or previous step in collections creation an event is logged in the "collections" schema with event_name "back", a funnel id, and the "source" of this is equivalent to the page they are on: start, name, etc.

Trello card: xV4FZKGl

• column: Must have