Add support for Django 6.0

[dchimeno]

Currently running project tests with django==6.0a1 fails with

  File "/usr/local/lib/python3.12/site-packages/django_tasks/backends/database/migrations/0005_alter_dbtaskresult_priority_and_more.py", line 6, in <module>
    class Migration(migrations.Migration):
  File "/usr/local/lib/python3.12/site-packages/django_tasks/backends/database/migrations/0005_alter_dbtaskresult_priority_and_more.py", line 19, in Migration
    constraint=models.CheckConstraint(
               ^^^^^^^^^^^^^^^^^^^^^^^
TypeError: CheckConstraint.__init__() got an unexpected keyword argument 'check'
make: *** [Makefile:23: test] Error 1
```

```bash
django-tasks                  0.8.1
```

would be great to upload a new release with the warning fixed for 5.2, or directly support 6.0.

[hakib]

You need to rename check= to condition=. However, to issue a proper PR you need to handle both Django versions I guess.

[mportesdev]

It seems that simply replacing check with condition breaks the migration 0005 in Django 4.2 which is still supported (and will be until April 2026).

A conditional test of Django version (something very similar to b12159d) might be necessary to make the migration 0005 compatible with both Django 4.2 and 6.0.