Get Datasets v1.2

Retrieve the list of available datasets that can be queried. Returns each dataset's machine-readable name (used in subsequent dataset API calls) and its human-readable label. Use the returned name values with POST /api/v1/datasets/{datasetName} to query data, and GET /api/v1_2/datasets/{datasetName}/fields to discover available fields. V1.2 endpoint: error responses use RFC 7807 application/problem+json.