* Adding ability to hide posts.
- Adds an post/hide API route.
- Adds a `show_hidden` (default false) to `GetPosts`.
- Adds a `hidden` field to `PostView`.
- Removes the single `post_id` from MarkPostAsRead.
- Fixes#1403
* Add a check to make sure hidden field is true.
* Fixing test.
* Add back semicolon