It's mostly an internal thing anyway and can be removed in 3.0.0

Improvements to HTTP requests

fix: correct ProjectFile.decode() documentation

Fix all issues reported by running: tox -e pep8 and enable pep8 as a linter check

ProjectFile.decode() returns 'bytes' and not 'str'.

Update the method's doc-string and add a type-hint.

ProjectFile.decode() returns the result of a call to
base64.b64decode()

The docs for that function state it returns 'bytes':
https://docs.python.org/3/library/base64.html#base64.b64decode

Fixes: #1403

If we want to update email, avatar and do not send email
confirmation change (`skip_reconfirmation` = True), `MultipartEncoder`
will try to encode everything except None and bytes. So it tries to encode bools.
Casting bool's values to their stringified int representation fix it.

fix(types): prevent __dir__ in RestObject from producing duplicates

chore: remove unused function sanitize_parameters()

fix: correct some type-hints in gitlab/mixins.py