Overview
Users should be able to pin their favorite tags to their blog.
Implementation idea
Create a pins table that includes all pinned items for a collection. Also consider T495: List all tags on a blog implementation if we go with that.
| collection_id | tag | post_id | pinned_position |
Design
On the /tags/{tag} page, add an option at / near the top of the page to "pin". If a tag is already pinned, this should say "unpin".