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
d96be4907e