Implement server OnError() hook

Example:

rpcServer := proto.NewVideoServer(app.Rpc)

rpcServer.OnError = func(r *http.Request, err *proto.WebRPCError) {
	ctx := r.Context()

	// Log error with request log
	httplog.LogEntrySetField(ctx context.Context, "webrpcError", err.Error())

	// Report crucial DB errors to Sentry
	var pgErr *pgconn.PgError
	if errors.As(err, &pgErr) {
		// https://www.postgresql.org/docs/16/errcodes-appendix.html
		if strings.HasPrefix(pgErr.Code, "42") {
			sentry.CaptureException(err)
		}
	}

	// Add requestID to error message itself.
	rpcErr.Message = fmt.Sprintf("%s (requestID: %v)", rpcErr.Message, middleware.GetReqID(ctx))

	// Hide error details from users in production.
	if app.Config.Environment.IsProduction() {
		rpcErr.Cause = ""
	}
}

errors.go.tmpl

@@ -60,7 +60,7 @@ func ErrorWithCause(rpcErr WebRPCError, cause error) WebRPCError {
 	return rpcErr.WithCause(cause)
 }
 
-{{- if $opts.errorStackTrace -}}
+{{if $opts.errorStackTrace -}}
 func (e WebRPCError) StackFrames() []uintptr {
 	return e.frame.frames[:]
 }