Description

When using a record struct in the generic TKey of a Dictionary, when an error of fluent assertion is generated, the .ToString() method is called which generates the following output:
MyStruct{ MyProperty1 = "MyProperty1", MyProperty2 = "MyProeprty2", ... }

One can see that using a ToString() on a record generates the characters { and } in the returned string.
The returned string is then used in turn in the string.Format() method but will crash because it considers { and } as parameter injection.
I mean, a message like this : MyStruct{ MyProperty1 = "MyProperty1", MyProperty2 = "MyProeprty2", ... } is considered as MyStruct{ paramForFormatMethod }.
So fluent assertion tries to inject a param in the generated string from the record struct.
(the example will help clarify)

Reproduction Steps

public readonly record struct MyRecordStruct
{
    public string MyProperty { get; init; }
}

[Fact]
public void myTest()
{
    var dict = new Dictionary<MyRecordStruct, MyRecordStruct>();
    var dict2 = new Dictionary<MyRecordStruct, MyRecordStruct>();

    var key = new MyRecordStruct() { MyProperty = "MyKey" };

    dict.Add(key, new MyRecordStruct());
    dict2.Add(key, new MyRecordStruct() { MyProperty = ""});

    dict2.Should().BeEquivalentTo(dict);
}

Expected behavior

Expected property dict2[MyRecordStruct { MyProperty = MyKey }].MyProperty to be null, but found "".

Actual behavior

It generates the following error message :

 **WARNING** failure message 'Expected property dict2[MyRecordStruct { MyProperty = MyKey }].MyProperty to be {0}, but found {1}.' could not be formatted with string.Format
   at System.Text.ValueStringBuilder.AppendFormatHelper(IFormatProvider provider, String format, ReadOnlySpan`1 args)
   at System.String.FormatHelper(IFormatProvider provider, String format, ReadOnlySpan`1 args)
   at System.String.Format(IFormatProvider provider, String format, Object[] args)
   at FluentAssertions.Execution.MessageBuilder.FormatArgumentPlaceholders(String failureMessage, Object[] failureArgs)

Regression?

No response

Known Workarounds

No response

Configuration

• FluentAssertions Version="6.12.0"
• .NET8