[Two migrants rest next to containers at a makeshift camp for refugees and migrants at the Greek-Macedonian border near the village of Idomeni]COPENHAGEN/BRUSSELS (Reuters) - Denmark extended temporary controls at its border with Germany on Monday, imposed to help control an influx of migrants, as the European Commission confirmed it would shortly authorise more such extensions within the passport-free Schengen zone. Seven members of the Schengen zone, including Germany and Denmark, have introduced temporary border controls after more than one million migrants entered the European Union last year, mostly via Greece. The European Commission, struggling to prevent the collapse of the Schengen accord, is expected this month to allow EU member states to retain the emergency border checks, which are due to expire in May, for a while longer.