Is your feature request related to a problem? Please describe.
I have an API exposed via different protocols (connect, grpc and connect-gateway/http). This API is auth protected (Bearer token in header or via Cookie-based session) and I'm using middlewares for that. I'd like to return helpful errors (missing, invalid, expired bearer token for example) for all of these APIs. Thus, the ErrorWriter is almost the perfect tool.

One thing I do not really want to enforce is setting an apropriate Content-Type in the request - for example if someone just wants to test an API endpoint via the Browser and the content-type is not set the ErrorWriter would not work because it's missing the Content-Type header with the protocol information.

Describe the solution you'd like

I would like to have a little bit more control (e.g. an extra HandlerOption) when constructing a new ErrorWriter, so that I could configure the ErrorWriter to fallback to writing JSON if no header is set.

Describe alternatives you've considered
I could inject the Content-Type header when no Content-Type header is set. It is a bit silly to do so, because the sole purpose would be to trick the ErrorWriter to write JSON.

Additional context

// In my middleware somewhere...
// This condition will evaluate to false if no Content-Type is set (e.g. request from the Browser), thus no error will be written by my ErrorWriter
if errorWriter.IsSupported(r) {
	err := apierrors.NewConnectError(
		connect.CodeUnauthenticated,
		errors.New("no bearer token found in authorization header"),
		apierrors.NewErrorInfo(commonv1alpha1.Reason_REASON_NO_AUTHENTICATION_TOKEN.String()),
	)
	_ = errorWriter.Write(w, r, err)
	return
}

errorWriter.Write() will only work if a known Content-Type header is set. Maybe there's a good reason why this should always be enforced, but I wouldn't know what reason that is.