Donald Trump has become Brussels’ inadvertent poster child for bonds issued by the EU. Not because the U.S. president is a fan of the EU. But because his trade tariffs and erratic foreign policy, ranging from threats to annex Greenland to waging war in the Middle East, are driving spooked investors to buy more EU debt. It is welcome news for the European Commission as it scales up its planned debt issuance to take on new tasks such as spending on its defense and supporting Ukraine’s resistance against Russian invasion.  [...]