Investigate ISpanFormattable

[Corniel]

It is far from trivial to support it, and I see no way to avoid double implementations. Specially supporting ICustomFormatter is potential challenging, but I gave Issue #244 a try.

The implementation for Guid was a bit of an inspiration.

[Corniel]

@sonnemaf I gave it a second go. I think I;'ll will slowly add them.

[Sjaaky]

Calling StringFormatter.TryApplyCustomFormatter() and copying the formatted string into a span kinda defeats the purpose of Span's, doesn't it?

[Corniel]

Calling StringFormatter.TryApplyCustomFormatter() and copying the formatted string into a span kinda defeats the purpose of Span's, doesn't it?

You don't gain anything from using TryFormat() in those scenario's, that's true. But if the behavior should be the same for both ToString() and TryFormat().

The thing that I did not find yet, if it is recommended to implement it, if there is nothing to be gained. What could be the case for at least a part of the string based SVO's.