Add string-option for ignoring newline style

[jnyrup]

Background and motivation

Split of from #2496 to ease review.

Some operating systems (Windows) use \r\n as newlines while others (Unix-based) use \n.

In some text-based protocol it's well-defined which type of newline should be used and one would explicitly test that.

var subject = GetValue("a", "b");
subject.Should().Be("a\r\nb");

Manually specifying newlines in tests is cumbersome and easily becomes less readable.
So in all remaining tests we simply wants to test that some newline is used.
Instead of explicitly specifying the newline character

var subject = GetValue();
subject.Should().Be("some\r\nvalue");

it would be a nice to write the tests using verbatim string literals

var subject = GetValue();
subject.Should().BeEquivalentTo(@"some
value");

or even more readable with the C# 11 raw string literals

var subject = GetValue();
subject.Should().BeEquivalentTo("""
    some
    value
    """);

API Proposal

public EquivalencyAssertionOptions<T> IgnoringNewlineStyle()
{
    // This will replace "\r\n" with "\n" in actual and expected before comparison
    return this;
}

API Usage

var windows = "a\r\nb";
var linux = "a\nb"

windows.Should().BeEquivalentTo(linux, o => o.IgnoringNewlineStyle());

Alternative Designs

No response

Risks

No response

Are you willing to help with a proof-of-concept (as PR in that or a separate repo) first and as pull-request later on?

No

[jnyrup]

I'm good with this

[dennisdoomen]

Me too