Update or remove 'Converters and codecs' article

[parlough]

Page URL

https://dart.dev/articles/archive/converters-and-codecs

Page source

https://github.com/dart-lang/site-www/tree/main/src/_articles/archive/converters-and-codecs.md

Describe the problem

The article has been marked as obsolete for a long time, but still is hosted and provides valuable information.

Expected fix

Either remove the article or update it for modern standards:

• Remove extra "article information (publish date, up-front authors, etc)
• Update text and code samples for modern Dart language (^3.4) and library changes
  • Also use newer lints and analyzer language modes
• Add code excerpts and tests for code samples
• Reduce amount of long text (more focused)
• Copy edit and update for modern GSG/our writing guidelines
• Update formatting/style for our current site guidelines
• After previous steps, remove the obsolete
• Find home in sidenav

[parlough]

@lrhn This old Converters and codecs article has been sitting, marked as obsolete, on the site for a long time now with outdated samples and perhaps inaccurate text.

Do you think you could take a quick look to see if it's worth me updating and cleaning it up? Or better to just drop in its current state?

[lrhn]

A quick look at the article doesn't show anything particularly wrong. The JsonCodec part mentions the toEncodable parameter, which I think was the most recent change, so it's probably up-to-date.

It's not a library that has had many changes.
I think there are places where I'd phrase things differently, or maybe focus differently, but the actual content is fine. It's not because anything is outdated.

Are you aware of any particular issues with the content?