curl --request GET \
  --url https://api.hubapi.com/properties/v1/contacts/groups/named/{groupName}

{
  "name": "<string>",
  "displayName": "<string>",
  "displayOrder": 123,
  "hubspotDefined": true,
  "properties": [
    {
      "name": "<string>",
      "label": "<string>",
      "description": "<string>",
      "groupName": "<string>",
      "type": "string",
      "fieldType": "textarea",
      "options": [
        {
          "description": "<string>",
          "label": "<string>",
          "value": "<string>",
          "displayOrder": 123,
          "hidden": true,
          "readOnly": true,
          "doubleData": 123
        }
      ],
      "displayOrder": 123,
      "formField": true,
      "readOnlyValue": true,
      "readOnlyDefinition": true,
      "hidden": true,
      "mutableDefinitionNotDeletable": true,
      "favorited": true,
      "favoritedOrder": 123,
      "calculated": true,
      "externalOptions": true,
      "displayMode": "<string>",
      "deleted": true,
      "hubspotDefined": true,
      "createdAt": 123,
      "updatedAt": 123,
      "createdUserId": 123,
      "updatedUserId": 123
    }
  ]
}