Add a migration for updating the default chat model, update for existing users

src/khoj/database/migrations/0034_alter_chatmodeloptions_chat_model.py

@@ -0,0 +1,32 @@
+# Generated by Django 4.2.10 on 2024-04-02 10:54
+
+from django.db import migrations, models
+
+
+def update_chat_model(apps, schema_editor):
+    ChatModelOptions = apps.get_model("database", "ChatModelOptions")
+    for chat_model_option in ChatModelOptions.objects.filter(chat_model="mistral-7b-instruct-v0.1.Q4_0.gguf"):
+        chat_model_option.chat_model = "NousResearch/Hermes-2-Pro-Mistral-7B-GGUF"
+        chat_model_option.save()
+
+
+def reverse_update_chat_model(apps, schema_editor):
+    ChatModelOptions = apps.get_model("database", "ChatModelOptions")
+    for chat_model_option in ChatModelOptions.objects.filter(chat_model="NousResearch/Hermes-2-Pro-Mistral-7B-GGUF"):
+        chat_model_option.chat_model = "mistral-7b-instruct-v0.1.Q4_0.gguf"
+        chat_model_option.save()
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("database", "0033_rename_tuning_agent_personality"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="chatmodeloptions",
+            name="chat_model",
+            field=models.CharField(default="NousResearch/Hermes-2-Pro-Mistral-7B-GGUF", max_length=200),
+        ),
+        migrations.RunPython(update_chat_model, reverse_code=reverse_update_chat_model),
+    ]