Django-clickhouse-backend

- Fix reading settings in explain, pull request [13](https://github.com/jayvynl/django-clickhouse-backend/pull/13) by [mahdi-jfri](https://github.com/mahdi-jfri).
- Add toYYYYMM[DD[hhmmss]] functions.
- Fix str(queryset.query) when default database is not clickhouse.
- Fix [bug when save django model instance](https://github.com/jayvynl/django-clickhouse-backend/issues/9).
- Support [clickhouse-driver 0.2.6](https://github.com/mymarilyn/clickhouse-driver), drop support for python3.6.
- Support [Django 4.2](https://docs.djangoproject.com).
- Support [clickhouse JSON type](https://clickhouse.com/docs/en/sql-reference/data-types/json).

- Fix test db name when NAME not provided in DATABASES setting.
- Fix Enum error when provided an IntegerChoices value.
- Add document about multiple db settings.

- Add `return_int` parameter to `Enum[8|16]Field` to control whether to get an int or str value when querying from the database.
- Fix TupleField container_class.
- Add fields documentation.

- Add tests for migrations.
- Fix bytes escaping.
- Fix date and datetime lookup.
- Add documentations.
- Add lots of new field types:
- Float32/64
- [U]Int8/16/32/64/128/256
- Date/Date32/DateTime('timezone')/DateTime64('timezone')
- String/FixedString(N)
- Enum8/16
- Array(T)
- Bool
- UUID
- Decimal
- IPv4/IPv6
- LowCardinality(T)
- Tuple(T1, T2, ...)
- Map(key, value)

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- Add tests for backends.
- Remove redundant code.
- Correct database features.
- Fix bugs that find by new tests.

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- Adopt some testcase from django project.
- Fix bugs such as datetime escaping and update field use F expression.