no issue
- we try to store all urls as relative paths where possible in Ghost so that the `config.url` value can be changed
- all relative paths are stored as root-relative except for the `post.canonical_url` field which was storing subdirectory-relative paths
- adds a migration to put the subdirectory prefix onto any relative canonical_url paths
- updates the canonical_url input serialiser to keep the subdirectory rather than stripping it to match all other url fields
* Simplified db controller permissions options
The existing objects were confusing because they did the same thing as
setting permissions to true, but gave the impressions that something
special was happening/required.
* Added DB Backup Integration Role
This will allow us to assign certain api_keys this role, in order to
automate db backups
* Allowed admin api_keys to have configurable roles
This will allow keys for the admin api to do customised things such as db export
* Added ghost-backup integration to fixtures
* Added migrations for DB Backup Integration and role
