Refactor JSON parser

[nicoweidner]

We want a refactored parser using the new data model (available on https://github.com/spdx/tools-python/tree/refactor-python-tools).

Possible basic interface (maybe extract an abstract base class later) as follows. The parser class should use composition instead of inheritance.

class JsonParser:
    creation_info_parser: CreationInfoParser
    package_parser: PackageParser
    file_parser: FileParser
    <...>

    def parse(self, filename: str) -> Document:
        logger = Logger()
         with open(filename) as file:
             input_doc_as_dict = json.load(file)
         document: Document = creation_info_parser.parse(input_doc_as_dict, logger)
         document.packages = package_parser.parse(input_doc_as_dict.get("packages"), logger)
        <...>
        
        if logger.has_errors():
            raise SpdxParsingError(logger.get_errors())
        return document

[nicoweidner]

Given the changes in #306, we should adapt the structure slightly: creation_info_parser will return a CreationInfo object that we can use to instantiate Document

[meretp]

fixed with #366