Sqlmodelservice

Changes:

- Added `Service.update_item()`.
- Added `safe_commit()` utility.
- Updated docs.
- Moved all service exceptions to the `errors` module. They can still be imported directly from `sqlmodelservice`.

Changes:

- Added new utility methods: `all()`, `one()`, and `one_or_none()`.
- Added new exception: `MultipleResultsFound` that can be raised by `one()`.
- `get_all()` is considered deprecated, use `all()` instead.
- The lib is now more flexible in terms of the required SQLModel version (`>=0.0.14,<0.1`)
- Added some more tests.

More `Service.select()` overloads.

Changes:

- Upgraded `Service.exec()` typing to accept `Select`s as well.

Features:

- `add_to_session()` now allows both creation and editing (there's now a required `operation` argument as well).
- There's a new `_apply_changes_to_item()` hook where updates are applied to a given database item.

Upgrade to Pydantic v2 and SQLModel 0.0.12.