refs https://github.com/TryGhost/Team/issues/1071
We used `posts.visibility` originally to store visibility as `free|paid` with a character limit of 50. This same field was repurposed to store an NQL filter when member tiers is enabled. The NQL filter uses the slug of the tier name, which can easily create a filter longer than 50 characters, adding an unwanted limitation on number of tiers that can be added to post's visibility.
Going forward, we'd like to store the visibility of posts for tiers in a separate pivot table and instead store the value of `visibility` as `tiers` when restricting post access to specific tiers. This change -
- adds a new pivot table fixture for storing relation between posts and tiers
- adds a migration for creating the new table
- updates tests
refs https://github.com/TryGhost/Ghost/commit/b93e7d7f7c
Our CI wasn't running integration tests so this slipped through. When
adding a new table we must update the exporter to ensure it's exported,
and that means the tests need to be updated to check for it!
- some tests are necessarily driven from the db
- these are like unit tests, except they only make sense if using the db - else you have to stub too much to make them worthwhile
- for these rare but important cases, we have the clear concept of integration tests
