dev: re-split migrations into two different files (#2268)

* dev: split issue activity migration separate files

* dev: resplit migrations into two different files

* dev: changed the batch size

apiserver/plane/db/migrations/0046_auto_20230926_1015.py

@@ -0,0 +1,26 @@
+# Generated by Django 4.2.5 on 2023-09-26 10:15
+
+from django.db import migrations
+
+
+def update_issue_activity(apps, schema_editor):
+    IssueActivity = apps.get_model("db", "IssueActivity")
+    updated_issue_activity = []
+    for obj in IssueActivity.objects.all():
+        obj.epoch = int(obj.created_at.timestamp())
+        updated_issue_activity.append(obj)
+    IssueActivity.objects.bulk_update(
+        updated_issue_activity,
+        ["epoch"],
+        batch_size=5000,
+    )
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('db', '0045_auto_20230915_0655'),
+    ]
+
+    operations = [
+         migrations.RunPython(update_issue_activity),
+    ]