Manifest creation helper

[approxit]

What I've done:

• Implemented initial DTO for objects from schema drafts found in GAP4 and GAP5.
• Only dataclasses are used...
• ...but with .dict(by_alias) and .parse_obj(obj) methods that reflects methods found in pydantic as this kind of models are just pydantic aim
• Additionally .parse_imploded_obj(obj) to ease with providing nested structures
• Tests to have coverage for new code

As this kind of DTOs should be implemented in pydantic, this should be mentioned as work item in https://github.com/golemfactory/golem-core-python/issues/54.

Keep in mind, that parsing object is quite a complex task. This implementation is not mentioned to be so robust as pydantic's. .parse_obj(obj) is just "base minimum".

Also exploding nested dicts is very easy task, but supporting exploding dicts with lists... oh boy, code complexity explodes too... I'm not very happy how it turned out, but at least its working and its covered with tests.

[shadeofblue]

as mentioned in the original issue: https://github.com/golemfactory/yapapi/issues/1090

the ultimate goal here is to have a helper function able to generate a valid manifest with minimal, obligatory input, e.g.:

manifest = generate_manifest(
   {
      "payload": manifest_payload("sha3:05270a8a938ff5f5e30b0e61bc983a8c3e286c5cd414a32e1a077657"),
      "net.inet.out.urls": ["http://bor.golem.network"],
   }
)