Moves Gfycat to use API via site access key.
Adds cachetools as dependency to reuse API keys for Gfycat/Redgifs at 95% of their TTL. Include tests to verify caching.
Updates versions of requests/yt-dlp/black/isort/pytest.
Added default timeout to requests calls.
Adds validate-pyproject and blacken-docs to pre-commit as well as updates versions.
Coverage for direct gfycat links that redirect to redgifs. The redirect through the sites themselves are broken but this fixes that.
Coverage for o.imgur links and incorrect capitalisation of domains in download_factory.
Changed tests for direct as gfycat is handled by the gfycat downloader.
fix pornhub test as the previous video was removed.
Consolidates sane flake8 settings to pyproject with the Flake8-pyproject plugin.
Does not change logic of test workflow but allows base settings to live in pyproject for anyone using flake8 as an external linter (e.g. vscode)
Also fixes some flake8 errors that were not being picked up by current testing, mostly unused imports.
Coverage for direct links.
The direct link won't work because it will have the wrong auth anyway but this will at least end up with the right API call.
Attempt to fix#724
Narrows down characters available to extensions in the regex. Outside of 3 and 4, the only extensions that I can think of this doesn't hit are bz2 and 7z (which wasn't caught before).
Standardizes shebang and coding declarations.
Coding matches what's used by install tools such as pip(x).
Removes a few init files that were not needed.
Add check to verify token was received.
Update headers sent to content API.
Add availability check for videos to resolve last part of #472 where only SD version is available.
Cover edge cases that shouldn't ever happen but probably will sometime.
Also included Imgur changes to cover similar situations of malformed/redirected links.
API seems to return incorrect signature value when sending header. Other fixes seems to have worked temporarily but have stopped working so they're removed.
