Apply Template to Campaign
==========================

+-------------------------------------------------------------------------+-------------------+-----------------+
| URL                                                                     | Required Values   | HTTP Methods    |
+=========================================================================+===================+=================+
| https://app.tingting.io/api/v1/survey-templates/<id>/apply-to-campaign/ | campaign_id       |      POST       |
+-------------------------------------------------------------------------+-------------------+-----------------+

Applies a survey template to an existing SURVEY campaign. Replace ``<id>`` with the template ID.

This action:

- Copies ``voice`` and ``length_factor`` from the template to the campaign.
- Deletes all existing steps from the campaign's survey.
- Creates new ``SurveyStep`` records from the template's ``content``.

**Request Body:**

+-------------+---------+----------+-------------------------------------------------------------------+
| Field       | Type    | Required | Description                                                       |
+=============+=========+==========+===================================================================+
| campaign_id | integer | Yes      | ID of the target campaign. Must be a SURVEY campaign owned by the |
|             |         |          | user.                                                             |
+-------------+---------+----------+-------------------------------------------------------------------+

Sample Request:

.. code-block:: json

    {
      "campaign_id": 42
    }

Sample Response — Success (201 Created):

.. code-block:: json

    {
      "message": "Template applied successfully.",
      "steps": [
        {
          "id": 101,
          "order": 0,
          "content_type": "say",
          "response_type": "dtmf",
          "input_name": "rating",
          "audio_file": null,
          "survey": 15
        },
        {
          "id": 102,
          "order": 1,
          "content_type": "info",
          "response_type": "none",
          "input_name": "outro",
          "audio_file": null,
          "survey": 15
        }
      ]
    }

Sample Response — Partial success, some steps failed (207 Multi-Status):

.. code-block:: json

    {
      "created": [
        { "id": 103, "order": 0 }
      ],
      "errors": [
        { "content_type": ["This field is required."] }
      ]
    }

**Error Responses (400 Bad Request):**

Missing ``campaign_id``:

.. code-block:: json

    { "error": "campaign_id is required." }

Campaign is not a SURVEY type:

.. code-block:: json

    { "error": "Template can only be applied to SURVEY campaigns." }

Template has no steps:

.. code-block:: json

    { "error": "Template has no steps to apply." }

**Error Responses (404 Not Found):**

Template not found or not owned by user:

.. code-block:: json

    { "detail": "No SurveyTemplate matches the given query." }

Campaign not found:

.. code-block:: json

    { "error": "Campaign not found." }