Hack around app label rename

Probably the shadiest/trickest part of this upgrade - we have to keep
existing migration history in mind to avoid running them twice (as
those would crash out), but we must assume this SQL will also run
when the new dependencies are set up and that would incorrectly mark
the external package migrations as belonging to the legacy app.

Therefore, we strictly limit the migrations that may be renamed to the
ones that are known - the timestamps added by django definitely help
here.

The digid-eherkenning.oidc migrations also start with a squashed
migration, so there is no collision on the 0001_initial migration 🎉

src/digid_eherkenning_oidc_generics/apps.py

@@ -1,8 +1,36 @@
+from contextlib import suppress
+
 from django.apps import AppConfig
+from django.db import OperationalError, ProgrammingError, connection
 from django.utils.translation import gettext_lazy as _
 
 
 class DigiDeHerkenningOIDCAppConfig(AppConfig):
     name = "digid_eherkenning_oidc_generics"
     verbose_name = _("DigiD & eHerkenning via OpenID Connect")
     label = "digid_eherkenning_oidc_generics_legacy"
+
+    def ready(self):
+        # Hook into the app registry to update the django_migrations table
+        # *before* we run migrations.
+        with suppress(OperationalError, ProgrammingError):
+            rename_app_label()
+
+
+def rename_app_label():
+    with connection.cursor() as cursor:
+        # uses explicit query names so that we don't accidentally rwrite the
+        # new digid_eherkenning.oidc migrations
+        query = """
+            UPDATE django_migrations
+            SET app = 'digid_eherkenning_oidc_generics_legacy'
+            WHERE app = 'digid_eherkenning_oidc_generics'
+            AND (
+                name = '0001_initial'
+                OR name = '0002_auto_20240109_1055'
+                OR name = '0003_alter_openidconnectdigidconfig_oidc_exempt_urls_and_more'
+                OR name = '0004_alter_openidconnectdigidconfig_table_and_more'
+                OR name = '0001_legacy'
+            )
+        """
+        cursor.execute(query)