I’ve added an ab_variant column to the dp_messages table in Supabase.

Goal:
- Let the /api/messages endpoint accept an optional "ab_variant" field
- Store it in dp_messages via insert_message()
- This will be used for A/B testing Lia's objection-handling messages.

Please update the backend as follows.

1) In app/db.py:

Find the existing insert_message function. It currently looks roughly like:

  async def insert_message(
      conversation_id: str,
      direction: str,
      channel: str,
      sender: str,
      message_body: str,
      template_key: str | None = None,
      mode: str | None = None,
  ) -> None:
      ...

Update it to accept an optional ab_variant parameter and insert into the new column. For example:

  async def insert_message(
      conversation_id: str,
      direction: str,
      channel: str,
      sender: str,
      message_body: str,
      template_key: str | None = None,
      mode: str | None = None,
      ab_variant: str | None = None,
  ) -> None:
      import uuid
      conv_uuid = uuid.UUID(conversation_id)
      conn = await get_conn()
      try:
          await conn.execute(
              """
              insert into dp_messages (
                  conversation_id,
                  direction,
                  channel,
                  sender,
                  message_body,
                  template_key,
                  mode,
                  ab_variant
              )
              values ($1, $2, $3, $4, $5, $6, $7, $8)
              """,
              conv_uuid,
              direction,
              channel,
              sender,
              message_body,
              template_key,
              mode,
              ab_variant,
          )
      finally:
          await release_conn(conn)

Make sure the column order in SQL matches the parameters.

2) In app/main.py:

Find the /api/messages POST handler. It currently pulls fields from payload like:

  template_key = payload.get("template_key")
  mode = payload.get("mode")

Extend it to read ab_variant and pass it through:

  ab_variant = payload.get("ab_variant")

Then update the call to insert_message to include this new parameter:

      await insert_message(
          conversation_id=conversation_id,
          direction=direction,
          channel=channel,
          sender=sender,
          message_body=message_body,
          template_key=template_key,
          mode=mode,
          ab_variant=ab_variant,
      )

3) Restart the server and test:

- POST /api/messages with a JSON body like:

  {
    "conversation_id": "<a-valid-uuid>",
    "message_body": "Test objection handling message",
    "mode": "objection_handling",
    "template_key": "oh_variant_1",
    "ab_variant": "oh_variant_1",
    "channel": "whatsapp",
    "direction": "outbound",
    "sender": "lia"
  }

- Confirm 200 OK.
- Check the database:

  select mode, template_key, ab_variant, message_body
  from dp_messages
  order by created_at desc
  limit 5;

You should see the ab_variant column populated correctly.