Get custom column list

{
  "type": "object",
  "required": [
    "customColumns",
    "links"
  ],
  "properties": {
    "customColumns": {
      "type": "array",
      "items": {
        "type": "object",
        "description": "The custom column configuration",
        "required": [
          "id",
          "userColumName",
          "configuration",
          "links"
        ],
        "properties": {
          "catalogColumnDependencies": {
            "type": "array",
            "items": {
              "type": "string",
              "description": "The catalog column name"
            }
          },
          "configuration": {
            "type": "object",
            "description": "Indicates the configuration applied on the column (catalog or custom) during the importation process.",
            "required": [
              "columnImportance",
              "columnDataType"
            ],
            "properties": {
              "beezUPColumnName": {
                "type": "string",
                "description": "The BeezUP column name"
              },
              "canBeTruncated": {
                "type": "boolean",
                "description": "If the size of the value is greater than the limit we can truncate the value instead of failing..."
              },
              "columnCultureName": {
                "type": "string",
                "description": "If non null, culture used to parse the value to the storage type of this column\\r\\n will be used for parsing and for consolidation proces"
              },
              "columnDataType": {
                "type": "string",
                "description": "Data type of the column, will be used for parsing and for consolidation proces",
                "enum": [
                  "String",
                  "Url",
                  "Text",
                  "Decimal",
                  "DateTime",
                  "Int",
                  "SpecialInt",
                  "InStock",
                  "Unknown",
                  "ImageUrl"
                ]
              },
              "columnFormat": {
                "type": "string",
                "description": "If non null, format used to parse the value to the storage type of this column\\r\\n will be used for parsing and for consolidation proces"
              },
              "columnImportance": {
                "type": "string",
                "description": "Importance of the column",
                "enum": [
                  "Required",
                  "Recommended",
                  "Optional"
                ]
              },
              "displayGroupName": {
                "type": "string",
                "description": "Indicate the display group name where the column must be putted"
              }
            }
          },
          "id": {
            "type": "string",
            "format": "guid",
            "description": "The catalog column identifier"
          },
          "links": {
            "type": "object",
            "required": [
              "save",
              "delete",
              "rename",
              "expression",
              "saveExpression"
            ],
            "properties": {
              "delete": {
                "type": "object"
              },
              "expression": {
                "type": "object"
              },
              "rename": {
                "type": "object"
              },
              "save": {
                "type": "object"
              },
              "saveExpression": {
                "type": "object"
              }
            }
          },
          "userColumName": {
            "type": "string",
            "description": "Column named by the user"
          }
        }
      }
    },
    "links": {
      "type": "object",
      "required": [
        "self"
      ],
      "properties": {
        "add": {
          "type": "object"
        },
        "self": {
          "type": "object"
        }
      }
    }
  }
}