**- Added extensive docstring coverage to ReceiptModel and related classes:**

  - Documented all public methods within `ReceiptModelAbstract`, `ReceiptModelManager`, and `ReceiptModelQuerySet` using the NumPy docstring style.
  - Enhanced clarity on receipt operations, query filters, validation, navigation, and lifecycle management methods.

**- Introduced additional dependencies in `pyproject.toml` for documentation generation:**
  - Added `myst-parser`, `sphinx`, and `renku-sphinx-theme` to support extended documentation requirements.

**- Updated `docs/source/models.rst` for receipt model inclusion:**
  - Integrated `ReceiptModel` documentation under the `models` section, ensuring visibility in the generated docs.

**- Synced dependency updates with `uv.lock`:**
  - Reflected new dev dependencies (`myst-parser`, `sphinx`, `renku-sphinx-theme`) in lock file for consistency.

### **Summary**
Added comprehensive documentation across the `ReceiptModel` implementation and its related classes. Extended `pyproject.toml` with dependencies for advanced document generation. Improved developer resources by linking receipt functionalities to the docs.

### **Backwards Compatibility**
No breaking changes introduced; only enhanced documentation and dependencies for development.

Author: elarroba