Replace named tuples with dataclasses and move JSON conversion logic to the base classes

Named tuples were never really adequate for this since the order aspect of them doesn't make sense.
Further, named tuples don't support multiple inheritance. This meant that the objects returned by get_items() were not actually Items, for example. Since Python 3.9, such named tuples cannot be created anymore.

Fixes #111

snscrape/modules/twitter.py

@@ -1,4 +1,5 @@
 import bs4
+import dataclasses
 import datetime
 import email.utils
 import itertools
@@ -17,7 +18,8 @@ logger = logging.getLogger(__name__)
 _API_AUTHORIZATION_HEADER = 'Bearer AAAAAAAAAAAAAAAAAAAAANRILgAAAAAAnNwIzUejRCOuH5E6I8xnZz4puTs=1Zv7ttfk8LF81IUq16cHjhLTvJu4FA33AGWWjCpTnA'
 
 
-class Tweet(typing.NamedTuple, snscrape.base.Item):
+@dataclasses.dataclass
+class Tweet(snscrape.base.Item):
 	url: str
 	date: datetime.datetime
 	content: str
@@ -49,39 +51,45 @@ class Medium:
 	pass
 
 
-class Photo(typing.NamedTuple, Medium):
+@dataclasses.dataclass
+class Photo(Medium):
 	previewUrl: str
 	fullUrl: str
 	type: str = 'photo'
 
 
-class VideoVariant(typing.NamedTuple):
+@dataclasses.dataclass
+class VideoVariant:
 	contentType: str
 	url: str
 	bitrate: typing.Optional[int]
 
 
-class Video(typing.NamedTuple, Medium):
+@dataclasses.dataclass
+class Video(Medium):
 	thumbnailUrl: str
 	variants: typing.List[VideoVariant]
 	duration: float
 	type: str = 'video'
 
 
-class Gif(typing.NamedTuple, Medium):
+@dataclasses.dataclass
+class Gif(Medium):
 	thumbnailUrl: str
 	variants: typing.List[VideoVariant]
 	type: str = 'gif'
 
 
-class DescriptionURL(typing.NamedTuple):
+@dataclasses.dataclass
+class DescriptionURL:
 	text: str
 	url: str
 	tcourl: str
 	indices: typing.Tuple[int, int]
 
 
-class User(typing.NamedTuple, snscrape.base.Entity):
+@dataclasses.dataclass
+class User(snscrape.base.Entity):
 	# Most fields can be None if they're not known.
 
 	username: str