feat: add support for fiber.ErrorHandler logging

[samber]

This PR allows to move the logger into *fiber.ErrorHandler:

Use either:

• the middleware
• the error handler (prefered)

NewXXX constructors have been renamed to NewMiddlewareXXX. Previous functions are marked as deprecated.

Via error handler

app := fiber.NewMiddleware(fiber.Config{
        // ...
    ErrorHandler: slogfiber.NewErrorHandler(logger.WithGroup("http")),
})

Via middleware

app.Use(slogfiber.NewMiddleware(logger))

[codecov-commenter]

Codecov Report

Attention: 147 lines in your changes are missing coverage. Please review.

Comparison is base (38a183c) 0.00% compared to head (bfa4885) 0.00%.

Files	Patch %	Lines
middleware.go	0.00%	87 Missing :warning:
error-handler.go	0.00%	39 Missing :warning:
config.go	0.00%	15 Missing :warning:
deprecated.go	0.00%	6 Missing :warning:

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Additional details and impacted files

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[daenney]

Sorry, it took me a bit longer to check on this.

The Error handler works and now all the context attributes I set do show up in the log line. That's great.

However, there's still two issues:

• the status= in the log line still reports 200 on a 404
• on an explicit route that just does a return fmt.Errorf("some error"), I also still get status=200 and the same happens with a fiber.NewError() call
• the HTTP status code from the handler is always 500, instead of the value in fiber.Error.Code

Also, for requests that are found, this no longer logs anything (since the error handler never executes). That makes sense, but it makes me wonder why there's the "error handler is now preferred" in the README since it seems like you would need both?

I'm really puzzled by the status thing since that's definitely not slogfiber messing it up. It's just the value on ctx.Response().StatusCode() which I really don't expect to be a 200 if we're in the error handler. My guess is that in the error handler this has to be explicitly extracted from the err passed to it, instead of using c.Response().StatusCode() since the error handler is expected to write the reply on the wire.

[UncleVic]

I think so, we should handle an error like that

        status := c.Response().StatusCode()
        var e *fiber.Error
        if errors.As(err, &e) {
            status = e.Code
        }

[samber]

Closing in favor of #19