Specify an `Index` for the id (`Item`) and Slug fields together.
Slug>>#gtLinksFor:
~
MELÉ, Antonio, 2020. Django 3 By Example. 3rd ed. Packt Publishing. ISBN 978-1-83898-195-2.
> slug: A short label that contains only letters, numbers, underscores, or hyphens to be used for building beautiful SEO-friendly URLs.
In the Meta class of the Product model, you use the index_together meta option to specify an index for the id and slug fields together. You define this index because you plan to query products by both id and slug. Both fields are indexed together to improve performance for queries that utilize the two fields. [⇐ Slug>>#gtLinksFor:]