curl --request GET \
  --url https://api.virtuoussoftware.com/api/ContactIndividual/CustomCollections \
  --header 'Authorization: Bearer <token>'

[
  {
    "id": "<integer>",
    "entityType": "<string>",
    "createDateTimeUtc": "<dateTime>",
    "createdByUser": "<string>",
    "modifiedDateTimeUtc": "<dateTime>",
    "modifiedByUser": "<string>",
    "name": "<string>",
    "fields": [
      {
        "dataType": "<string>",
        "name": "<string>",
        "displayName": "<string>",
        "required": "<boolean>",
        "options": [
          "<string>",
          "<string>"
        ]
      },
      {
        "dataType": "<string>",
        "name": "<string>",
        "displayName": "<string>",
        "required": "<boolean>",
        "options": [
          "<string>",
          "<string>"
        ]
      }
    ]
  },
  {
    "id": "<integer>",
    "entityType": "<string>",
    "name": "<string>",
    "createDateTimeUtc": "<dateTime>",
    "createdByUser": "<string>",
    "modifiedDateTimeUtc": "<dateTime>",
    "modifiedByUser": "<string>",
    "fields": [
      {
        "dataType": "<string>",
        "name": "<string>",
        "displayName": "<string>",
        "required": "<boolean>",
        "options": [
          "<string>",
          "<string>"
        ]
      },
      {
        "dataType": "<string>",
        "name": "<string>",
        "displayName": "<string>",
        "required": "<boolean>",
        "options": [
          "<string>",
          "<string>"
        ]
      }
    ]
  }
]