The value of the cookie.
Must be a cookie-value as specified in RFC 6265.
The allowed characters in a cookie value are the visible ASCII characters, U+0021 (!) through U+007E (~) except the characters: ", ,, ; and \. Cookie values may be wrapped in a single pair of double quotes (U+0022, ").
String value
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https://api.dart.dev/stable/2.5.0/dart-io/Cookie/value.html