Necassary changes to create dim from json file

[MariusWirtz]

Allows this:

    month_dimension = tm1.dimensions.get(dimension_name="month")
    with open("raw/month.json", "w") as file:
        file.write(month_dimension.body)


    with open("raw/month.json") as file:
        month_dimension = Dimension.from_json(file.read())
    month_dimension.name = "NUK month"
    tm1.dimensions.update_or_create(month_dimension)