Django 5.1 Support - deprecated index_together

[whoisearth]

Fix pulled from Django 4.2 release notes here -

https://docs.djangoproject.com/en/5.1/releases/4.2/#deprecated-features-4-2

Migrating existing index_together should be handled as a migration. For example:

class Author(models.Model):
    rank = models.IntegerField()
    name = models.CharField(max_length=30)

    class Meta:
        index_together = [["rank", "name"]]

Should become:

class Author(models.Model):
    rank = models.IntegerField()
    name = models.CharField(max_length=30)

    class Meta:
        indexes = [models.Index(fields=["rank", "name"])]