🐛 Fix encoding data with None values and more

[karosc]

This addresses #118, inspired by the code in requests.

Essentially this PR will allow encoding any non-iterable object as string. This is a general solution to the specific problem in #118. Since None is not iterable, it is encoded "None". Similarly, any non-iterable object will be encoded as str(obj).

[Ousret]

the test only make sure the error does not occurs. we should verify that the "None" values are excluded.

[karosc]

@Ousret, you're totally right. I had how requests handles the None values totally wrong. I updated the PR and unit tests to check the values of the encoding as you suggested. I also wrote a short script to test that requests and niquests produce the same results when posting various python types:

import niquests
import requests

class Class:
        pass

class ClassStringable:
    def __str__(self):
        return "🔥arbClassStringable🔥"

url = "https://httpbin.org/post"
body = {
    "string": "string",
    "float": 0.01,
    "int": 100,
    "bool": True,
    "None": None,
    "plain_class": Class(),
    "stringable_class": ClassStringable(),
}

resp_re = requests.post(url, data = body)
resp_ni = niquests.post(url, data = body)


for key in ['args', 'data','files','form','json']:
    try:
        assert resp_re.json()[key] == resp_ni.json()[key]
    except AssertionError:
        print(resp_re.json()[key],'\n\n\n',resp_ni.json()[key])

[Ousret]

Almost there.