Parent ticket https://phabricator.wikimedia.org/T339334#9092727

In order to be able to store per-wiki statistics, introduce a WikiSiteInfo Eloquent model and add such info to the Wiki model, using a one to one relationship.

The fields of the WikiSiteInfo model should match the info returned from a siteinfo MediaWiki API call (when a field is not present it gets zeroed out):

"pages": int,
"articles": int,
"edits": int,
"images": int,
"users": int,
"activeusers": int,
"admins": int,
"jobs": int,
"cirrussearch-article-words": int

Also. a boolean field isFeatured is introduced at Wiki level.

Also. a text field description is introduced at Wiki level.

AC:

• The new WikiSiteInfo model is created and attached to the Wiki model
• The new isFeatured property is created on the Wiki model, defaulting to false
• The new description property is created on the Wiki model, defaulting to the empty string
• Migrations are created
• Applying the migration created all-zero data for each wiki