retrieve:
Return the details about the given Theme id.

list:
List all Theme objects.

GET /api/v1/themes/4/
HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "id": 4,
    "fr_label": "Ingénierie",
    "en_label": "Engineering",
    "de_label": "Ingenieurwissenschaften"
}