Tortoise-orm

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- fix: ``sqlite://:memory:`` in Windows thrown ``OSError: [WinError 123]``
- Support ``bulk_create()`` insertion of records with overridden primary key when the primary key is DB-generated
- Add ``queryset.exists()`` and ``Model.exists()``.
- Add model subscription lookup, ``Model[<pkval>]`` that will return the object or raise ``KeyError``

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- Fix bad import of ``basestring``
- Better handling of NULL characters in strings. Fixes SQLite, raises better error for PostgreSQL.
- Support ``.group_by()`` with join now

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- Support ``F`` expression in ``.save()`` now
- ``IntEnumField`` accept valid int value and ``CharEnumField`` accept valid str value
- Pydantic models get created with globally unique identifier
- Leaf-detection to minimize duplicate Pydantic model creation
- Pydantic models with a Primary Key that is also a raw field of a relation is now not hidden when ``exclude_raw_fields=True`` as it is a critically important field
- Raise an informative error when a field is set as nullable and primary key at the same time
- Foreign key id's are now described to have the positive-integer range of the field it is related to
- Fixed prefetching over OneToOne relations
- Fixed ``__contains`` for non-text fields (e.g. ``JSONB``)

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- Allow ``Q`` expression to function with ``_filter`` parameter on aggregations
- Add manual ``.group_by()`` support
- Fixed regression where ``GROUP BY`` class is missing for an aggregate with a specified order.

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- Added preliminary support for Python 3.9
- ``TruncationTestCase`` now properly quotes table names when it clears them out.
- Add model signals support
- Added ``app_label`` to ``test initializer(...)`` and ``TORTOISE_TEST_APP`` as test environment variable.

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.. warning::

This is a security fix release. We recommend everyone update.

Security fixes
^^^^^^^^^^^^^^

- Fixed SQL injection issue in MySQL
- Fixed SQL injection issues in MySQL when using ``contains``, ``starts_with`` or ``ends_with`` filters (and their case-insensitive counterparts)
- Fixed malformed SQL for PostgreSQL and SQLite when using ``contains``, ``starts_with`` or ``ends_with`` filters (and their case-insensitive counterparts)

Other changes
^^^^^^^^^^^^^

* Added support for partial models:

To create a partial model, one can do a ``.only(<fieldnames-as-strings>)`` as part of the QuerySet.
This will create model instances that only have those values fetched.

Persisting changes on the model is allowed only when:

* All the fields you want to update is specified in ``<model>.save(update_fields=[...])``
* You included the Model primary key in the ``.only(...)``

To protect against common mistakes we ensure that errors get raised:

* If you access a field that is not specified, you will get an ``AttributeError``.
* If you do a ``<model>.save()`` a ``IncompleteInstanceError`` will be raised as the model is, as requested, incomplete.
* If you do a ``<model>.save(update_fields=[...])`` and you didn't include the primary key in the ``.only(...)``,
then ``IncompleteInstanceError`` will be raised indicating that updates can't be done without the primary key being known.
* If you do a ``<model>.save(update_fields=[...])`` and one of the fields in ``update_fields`` was not in the ``.only(...)``,
then ``IncompleteInstanceError`` as that field is not available to be updated.

- Fixed bad SQL generation when doing a ``.values()`` query over a Foreign Key
- Added `<model>.update_from_dict({...})` that will mass update values safely from a dictionary
- Fixed processing URL encoded password in connection string