test for extra attributes for Semantics objects

cube.city.json

{
  "CityObjects": {
    "id-1": {
      "geometry": [
        {
          "boundaries": [
              [
                [
                  0,
                  1,
                  2,
                  3
                ]
              ],
              [
                [
                  4,
                  5,
                  0,
                  3
                ]
              ],
              [
                [
                  5,
                  6,
                  1,
                  0
                ]
              ],
              [
                [
                  6,
                  7,
                  2,
                  1
                ]
              ],
              [
                [
                  3,
                  2,
                  7,
                  4
                ]
              ],
              [
                [
                  7,
                  6,
                  5,
                  4
                ]
              ]
          ],
          "lod": "1.2",
          "semantics": {
            "surfaces" : [
              {
                "type": "WallSurface"
              }, 
              {
                "type": "RoofSurface",
                "slope": 66.6
              },
              {
                "type": "+ThermalSurface",
                "azimuth": 71.1
              }
            ],
            "values": [0, 0, 1, 2, 2, 1]
          },
          "type": "MultiSurface"
        }
      ],
      "attributes": {
        "function": "something"
      },
      "type": "GenericCityObject"
    }
  },
  "type": "CityJSON",
  "version": "2.0",
  "vertices": [
    [
      2000,
      1000,
      1000
    ],
    [
      1000,
      2000,
      1000
    ],
    [
      0,
      1000,
      1000
    ],
    [
      1000,
      0,
      1000
    ],
    [
      1000,
      0,
      0
    ],
    [
      2000,
      1000,
      0
    ],
    [
      1000,
      2000,
      0
    ],
    [
      0,
      1000,
      0
    ]
  ],
  "metadata": {
    "geographicalExtent": [
      -1.0,
      -1.0,
      0.0,
      1.0,
      1.0,
      1.0
    ]
  },
  "transform": {
    "scale": [
      0.001,
      0.001,
      0.001
    ],
    "translate": [
      -1.0,
      -1.0,
      0.0
    ]
  },
  "extensions": {
    "Generic": {
      "url": "https://www.hugo.com",
      "version": "1.0"
    }
  }
}

thermal.ext.json

{
  "type": "CityJSONExtension",
  "name": "Thermal",
  "uri": "https://www.hugo.com",
  "version": "0.1.0",
  "versionCityJSON": "2.0",
  "description": "Extension to handle GenericCityObject; meant as a template to learn how to construct an Extension",
  "extraRootProperties": {},
  "extraAttributes": {},
  "extraCityObjects": {},
  "extraSemanticSurfaces": {
    "+ThermalSurface": {
      "type": "object",
      "properties": {
        "type": {
          "enum": [
            "+ThermalSurface"
          ]
        },
        "azimuth": {
          "type": "number"
        }
      },
      "required": [
        "type",
        "azimuth"
      ],
      "additionalProperties": false
    }
  }
}