Datajudge

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**New features**

- Implement :meth:`datajudge.WithinRequirement.add_functional_dependency_constraint`.

**Other changes**

- Improve error message when a :class:`~datajudge.DataReference` is constructed with a single column name instead of specifying a list of columns.

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**New features**

- Implement :meth:`datajudge.WithinRequirement.add_categorical_bound_constraint`.
- Extended :meth:`datajudge.WithinRequirement.add_column_type_constraint` to support column type specification using string format, backend-specific SQLAlchemy types, and SQLAlchemy's generic types.
- Implement :meth:`datajudge.WithinRequirement.add_numeric_no_gap_constraint`, :meth:`datajudge.WithinRequirement.add_numeric_no_overlap_constraint`,

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**Other changes**

- Ensure compatibility with ``sqlalchemy`` >= 2.0.

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**New features**

- Implement :meth:`datajudge.BetweenRequirement.add_max_null_fraction_constraint` and
:meth:`datajudge.WithinRequirement.add_max_null_fraction_constraint`.
- Implement :meth:`datajudge.BetweenRequirement.add_numeric_percentile_constraint` and
:meth:`datajudge.WithinRequirement.add_numeric_percentile_constraint`.

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**New features**

- Add partial and experimental support for db2 as a backend.

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**New features**

- Implement :meth:`~datajudge.BetweenRequirement.add_column_type_constraint`. Previously, only the ``WithinRequirement`` method existed.
- Implemented an option ``infer_pk`` to automatically retrieve and primary key definition as part of :meth:`datajudge.WithinRequirement.add_uniqueness_constraint`.
- Added a ``name`` parameter to all ``add_x_constraint`` methods of ``WithinRequirement`` and ``BetweenRequirement``. This will give pytest test a custom name.
- Added preliminary support for Impala.

**Other changes**

- Improve assertion error for :meth:`~datajudge.WithinRequirement.add_row_matching_equality_constraint`.