MediaTypeHeaderValue should ignore unknow parameters in MIME types

[enzian]

Description

When System.Net.Http.Headers.MediaTypeHeaderValue(string) is used to parse a MIME type which contains an unnecessary parameter like in image/png;charset=UTF-8 a format exception is thrown. While this modifier makes admittedly little sense, the IEEE spec explicity states that "MIME implementations must also ignore any parameters whose names they do not recognize"

Configuration

Reproduced in netcoreapp3.1, SDK version 3.1.300

Regression

[Fact]
public async Task TestImageWithCharset()
{
    new MediaTypeHeaderValue("image/png;charset=UTF-8");
}

[ghost]

Tagging subscribers to this area: @tannergooding
Notify danmosemsft if you want to be subscribed.

[ghost]

Tagging subscribers to this area: @dotnet/ncl
Notify danmosemsft if you want to be subscribed.

[dotnet-policy-service]

Due to lack of recent activity, this issue has been marked as a candidate for backlog cleanup. It will be closed if no further activity occurs within 14 more days. Any new comment (by anyone, not necessarily the author) will undo this process.

This process is part of our issue cleanup automation.