Adds deactivation date to user model

Also fixes django admin around saved lists

bookwyrm/migrations/0094_auto_20210911_1550.py

@@ -0,0 +1,39 @@
+# Generated by Django 3.2.4 on 2021-09-11 15:50
+
+from django.db import migrations, models
+from django.db.models import F, Value, CharField
+
+
+def set_deactivate_date(apps, schema_editor):
+    """best-guess for deactivation date"""
+    db_alias = schema_editor.connection.alias
+    apps.get_model("bookwyrm", "User").objects.using(db_alias).filter(
+        is_active=False
+    ).update(deactivation_date=models.F("last_active_date"))
+
+
+def reverse_func(apps, schema_editor):
+    """noop"""
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("bookwyrm", "0093_alter_sitesettings_instance_short_description"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="user",
+            name="deactivation_date",
+            field=models.DateTimeField(blank=True, null=True),
+        ),
+        migrations.AlterField(
+            model_name="user",
+            name="saved_lists",
+            field=models.ManyToManyField(
+                blank=True, related_name="saved_lists", to="bookwyrm.List"
+            ),
+        ),
+        migrations.RunPython(set_deactivate_date, reverse_func),
+    ]