Custom action to retrieve the summary of a Showcase instance.

Args: request (Request): The HTTP request object. pk (int): The primary key of the Showcase instance.

Returns: Response: The serialized summary of the Showcase instance.

GET /closecycle/api/showcase/summaries/?format=api
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "summaries": [
        {
            "id": 12,
            "name": "Agricultural Education",
            "region": "Västra Götalands län",
            "description": "",
            "involved_processes": []
        }
    ]
}