Summary
Allow a manifest's datasets to be specified as paths, allowing metadata to be gathered dynamically from these datasets instead of hard-coded in a manifest serialisation.
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Contents ([101](https://github.com/octue/twined/pull/101))
**IMPORTANT:** There are 2 breaking changes.
Enhancements
- **BREAKING CHANGE:** Make `Twine.available_strands` a set instead of a tuple
- Update manifest schema to allow path-only datasets
- Raise error if a dataset specified in a manifest strand of the twine is missing from the corresponding manifest
- Add `Twine.available_manifest_strands` property
Refactoring
- **BREAKING CHANGE:** Move dataset files tag checking into `octue-sdk-python` at `octue.runner.Runner._validate_dataset_file_tags`
Refactoring
- Move manifest and twine migrations into `migrations` subpackage
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