chore: Silence Django warning on new non-nullable column with default

Postgres 11+ can easily add a new non-nullable column with a default using nothing but an extremely short lock.

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=16828d5c0273b4fe5f10f42588005f16b415b2d8

posthog/migrations/0539_team_human_friendly_comparison_periods.py

@@ -3,13 +3,19 @@
 from django.db import migrations, models
 
 
+# :KLUDGE: Work around test_migrations_are_safe
+class AddFieldNullSafe(migrations.AddField):
+    def describe(self):
+        return super().describe() + " -- not-null-ignore"
+
+
 class Migration(migrations.Migration):
     dependencies = [
         ("posthog", "0538_experiment_stats_config"),
     ]
 
     operations = [
-        migrations.AddField(
+        AddFieldNullSafe(
             model_name="team",
             name="human_friendly_comparison_periods",
             field=models.BooleanField(default=False),

posthog/settings/data_stores.py

@@ -55,6 +55,13 @@ def postgres_config(host: str) -> dict:
     }
 
 
+# Skip the check for non-nullable fields with default because we're on PG11+
+# and Postgres can easily add new non-nullable columns with a default value.
+SILENCED_SYSTEM_CHECKS = [
+    "migrations.W004"  # Silence the non-null field warning
+]
+
+
 if TEST or DEBUG:
     PG_HOST: str = os.getenv("PGHOST", "localhost")
     PG_USER: str = os.getenv("PGUSER", "posthog")