closes#9314
* added fixtures for contributor role
* update post api tests to prevent contributor publishing post
* update permissible function in role/user model
* fix additional author code in invites
* update contributor role migration for knex-migrator v3
* fix paths in contrib migration
* ensure contributors can't edit or delete published posts, fix routing tests [ci skip]
* update db fixtures hash
* strip tags from post if contributor
* cleanup post permissible function
* excludedAttrs to ignore tag updates for now (might be removed later)
* ensure contributors can't edit another's post
* migration script for 1.21
refs #9178
- first iteration of tidying up the unit tests
- this is useful in the current stage, because if i move files in the server folder, i need a clean folder/file structure to detect which tests needs to move
- this is a simple cleanup to reflect the current server folder structure
