fmsg: add a shorthand for formatted With

[ghost]

TL;DR

A simple shorthand that combines fmsg.With() + fmt.Sprintf() for improved DX.

Why

First of all, great library!

But after writing this pattern (not exaggerating here) a thousands of times, I'm pretty sick of it:

err := ThingThatCanReturnError(id)
if err != nil{
    return fault.Wrap(err, fmsg.With(fmt.Sprintf("call ThingThatCanReturnError with id::%s", id)))
}

It's pretty verbose. But most annoyingly I have a linter that complains if a line is more than 150 characters long. And funnily enough that additional fmt.Sprintf is what gets it over the 150 pretty often (nope, can't just disable that).

So I'd like to add a shorthand for that operation. Just like there's fault.New and fault.Newf, I feel like there should be a fmsg.Withf function

[Southclaws]

I've actually been meaning to add this for ages, thanks! The same thing has annoyed me and I didn't get around to it!