Get custom column list

Example response

{
  "links": {
    "self": {
      "href": "/v2/user/catalogs/a42b780d-4585-4566-800e-4d77a4d6f8a3/customColumns",
      "method": "GET"
    },
    "add": {
      "href": "/v2/user/catalogs/a42b780d-4585-4566-800e-4d77a4d6f8a3/customColumns/{columnId}",
      "method": "POST",
      "parameters": {
        "columnId": {
          "type": "string",
          "required": true,
          "in": "path"
        },
        "request": {
          "type": "object",
          "required": true,
          "in": "body",
          "schema": "createCustomColumnRequest"
        }
      }
    }
  },
  "customColumns": [
    {
      "id": "8f6671d6-a9bc-4de0-a0c4-4643b0c3f871",
      "userColumName": "My SKU",
      "configuration": {
        "beezUPColumnName": "CategoryFirstLevel",
        "columnImportance": "Required",
        "columnDataType": "String",
        "columnCultureName": "fr-FR",
        "columnFormat": "MM/dd/yyyy",
        "displayGroupName": "Category"
      },
      "catalogColumnDependencies": [
        "SKU"
      ],
      "links": {
        "save": {
          "href": "/v2/user/catalogs/a42b780d-4585-4566-800e-4d77a4d6f8a3/customColumns/{columnId}",
          "method": "POST",
          "parameters": {
            "columnId": {
              "type": "string",
              "required": true,
              "in": "path"
            },
            "request": {
              "type": "object",
              "required": true,
              "in": "body",
              "schema": "createCustomColumnRequest"
            }
          }
        },
        "delete": {
          "href": "/v2/user/catalogs/a42b780d-4585-4566-800e-4d77a4d6f8a3/customColumns/5b56bb78-bc0b-485e-abd8-8db7eed995cb",
          "method": "DELETE"
        },
        "rename": {
          "href": "/v2/user/catalogs/a42b780d-4585-4566-800e-4d77a4d6f8a3/customColumns/5b56bb78-bc0b-485e-abd8-8db7eed995cb/rename",
          "method": "POST",
          "parameters": {
            "request": {
              "type": "object",
              "required": true,
              "in": "body",
              "schema": "changeUserColumnNameRequest"
            }
          }
        },
        "expression": {
          "href": "/v2/user/catalogs/a42b780d-4585-4566-800e-4d77a4d6f8a3/customColumns/5b56bb78-bc0b-485e-abd8-8db7eed995cb/expression",
          "method": "GET"
        },
        "saveExpression": {
          "href": "/v2/user/catalogs/a42b780d-4585-4566-800e-4d77a4d6f8a3/customColumns/5b56bb78-bc0b-485e-abd8-8db7eed995cb/expression",
          "method": "PUT",
          "parameters": {
            "request": {
              "type": "object",
              "required": true,
              "in": "body",
              "schema": "changeCustomColumnExpressionRequest"
            }
          }
        }
      }
    }
  ]
}