Add and document reencrypt_fields command

src/servala/core/management/commands/reencrypt_fields.py

@@ -0,0 +1,21 @@
+from django.core.management.base import BaseCommand
+from django.db import transaction
+
+from servala.core.models.service import ControlPlane
+
+
+class Command(BaseCommand):
+    help = "Re-encrypts all encrypted fields. Use when rotating SECRET_KEY/SALT"
+
+    def handle(self, *args, **options):
+        self.stdout.write("Starting re-encryption of ControlPlane objects...")
+
+        count = 0
+        with transaction.atomic():
+            for control_plane in ControlPlane.objects.all():
+                control_plane.save()
+                count += 1
+
+        self.stdout.write(
+            self.style.SUCCESS(f"Re-encrypted {count} ControlPlane objects")
+        )