add extractors for fantia and fanbox (#1459)

* add extractors for fantia and fanbox

* appease linter

* make docstrings unique

* [fantia] refactor post extraction

* [fantia] capitalize

* [fantia] improve regex pattern

* code style

* capitalize

* [fanbox] use BASE_PATTERN for url regexes

* [fanbox] refactor metadata and post extraction

* [fanbox] improve url base pattern

* [fanbox] accept creator page links ending with /posts

* [fanbox] more tests

* [fantia] improved pagination

* [fanbox] misc. code logic improvements

* [fantia] finish restructuring pagination code

* [fanbox] avoid making a request for each individual post when processing a creator page

* [fanbox] support embedded videos

* [fanbox] fix errors

* [fanbox] document extractor.fanbox.videos

* [fanbox] handle "article" and "entry" post types, all embeds

* [fanbox] fix downloading of embedded fanbox posts

scripts/supportedsites.py

@@ -208,6 +208,8 @@ AUTH_MAP = {
     "e621"           : "Supported",
     "e-hentai"       : "Supported",
     "exhentai"       : "Supported",
+    "fanbox"         : _COOKIES,
+    "fantia"         : _COOKIES,
     "flickr"         : _OAUTH,
     "furaffinity"    : _COOKIES,
     "idolcomplex"    : "Supported",