feat: Add OrFailIf extension method

[martin-hirsch]

Hello there,

This pull request introduces a new extension method, OrFailIf, to the Result class.

I hope you don't mind that I went ahead and created this pull request directly. I felt a separate discussion wasn't necessary since this addition is minor, straightforward, and self-explanatory.

I often find myself needing to split Result.Merge() statements to provide more detailed error messages, particularly for null checks. To avoid repetitive code in every validation, I believe this feature offers a clean and effective solution to that problem.

Looking forward to your feedback!

Best regards,
Martin

[Kilazur]

We made multiple extension methods at my job to deal with failures. I can't legally share it, but you may want to add methods that take a predicate as a parameter, that acts on the value of a Result, so you can fail if the value isn't valid contextually.

You can also add other signature of this method to follow the existing formats of methods acting on Result and Task, like Bind.

[martin-hirsch]

That's exactly what I always found myself doing. Creating or copying the same extension methods from over and over again.

This time I'll try to contribute. 🚀