Added a new tag field to each article.
Added a customer app and a product app.
When sending emails to subscribers:
- if a subscriber is not a customer, he is sent the entire message (with all the articles)
- if a subscriber is a customer, we will check the name of the products he owns against each article's tag. If they match, that article will not be added to the newsletter. We will only send articles whose tags do not match any owned products.
- if a subscriber is a customer and doesn't own any product (for some reason), he is sent the full message.