fix: remove use of deprecated cgi module

[adamchainz]

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Fixes #892 🦕

[adamchainz]

Comparison of the two approaches:

>>> import cgi <stdin>:1: DeprecationWarning: 'cgi' is deprecated and slated for removal in Python 3.13 >>> from email.message import Message >>> content_type = 'text/plain; charset=utf-8; other=something' >>> cgi.parse_header(content_type)[1] {'charset': 'utf-8', 'other': 'something'} >>> message = Message(); message['content-type'] = content_type; dict(message.get_params()[1:]) {'charset': 'utf-8', 'other': 'something'} 

[adamchainz]

Moved to HeaderParser, checked for equivalence on shell again:

>>> from email.parser import HeaderParser >>> content_type = 'text/plain; charset=utf-8; other=something' >>> msg = HeaderParser().parsestr("Content-Type: " + content_type) >>> dict(msg.get_params()[1:]) {'charset': 'utf-8', 'other': 'something'} 

[andrewsg]

Thank you for doing this! I'll have the tests run against this branch and we'll go from there.

[andrewsg]

Thank you!