Add support for Croissant RecordSet objects

[amercader]

From the new docs:

for resources that have been imported to the CKAN DataStore, the resource will also expose Croissant's RecordSet objects with information about the data fields (e.g. column names and types).

DataStore imported tables is the closest that CKAN has right now to a source for identifying the data structure of the data files hosted, and this info really adds value for integration with ML processes and pipelines.

---

To test this the DataStore needs to be configured and some data imported:

1. Set up the DataStore
2. Get some data, either by enabling and running the Xloader extension or by pushing data directly with a script like the following:

curl -X POST \
  'http://CHANGE_ME/api/3/action/datastore_create' \
  -H "Authorization: CHANGE_ME" \
  -H 'Content-Type: application/json' \
  -d '{
    "resource": {
      "package_id": "CHANGE_ME",
      "name": "Air quality",
      "description": "Test data"
    },
    "fields": [
      {
        "id": "measurement_id",
        "type": "text",
        "primary_key": true
      },
      {
        "id": "timestamp",
        "type": "timestamp"
      },
      {
        "id": "location_name",
        "type": "text"
      },
      {
        "id": "temperature_celsius",
        "type": "float"
      },
      {
        "id": "humidity_percent",
        "type": "float"
      },
      {
        "id": "pm25_concentration",
        "type": "float"
      }
    ],
    "records": [
      {
        "measurement_id": "AQ001",
        "timestamp": "2025-02-20T09:30:00",
        "location_name": "Downtown Station",
        "temperature_celsius": 22.5,
        "humidity_percent": 45.3,
        "pm25_concentration": 12.8
      },
      {
        "measurement_id": "AQ002",
        "timestamp": "2025-02-20T10:15:00",
        "location_name": "Industrial Zone",
        "temperature_celsius": 24.1,
        "humidity_percent": 42.7,
        "pm25_concentration": 18.5
      },
      {
        "measurement_id": "AQ003",
        "timestamp": "2025-02-20T11:00:00",
        "location_name": "Residential Area",
        "temperature_celsius": 21.8,
        "humidity_percent": 48.2,
        "pm25_concentration": 8.3
      }
    ],
    "primary_key": ["measurement_id"],
    "indexes": ["timestamp", "location_name"],
    "force": true
}'