Django-concurrency

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* add support do Django 5.x
* drop support python 3.9
* drop support django 3.x
* move to .pyproject.toml

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* BUG FIX: fixes check() implementation
* removes deprecatd MANUAL_TRIGGERS
* drop support Django 2.x
* drop support python 3.8

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* add support Django 4
* add support Python 3.10

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* Removes code producing DeprecationError
* add :setting:`AUTO_CREATE_TRIGGERS` and deprecate :setting:`MANUAL_TRIGGERS`
* add support for Postgres 13
* add ability to customise SQL to create triggers :setting:`TRIGGERS_FACTORY`

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* drop suppot django<3.0
* drop suppot Python<3.6

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* fixes packaging