Costa Rica said Thursday that it would accept 25 migrants deported from the United States per week as part of an agreement to help the Trump administration’s latest policy of deporting immigrants to “third countries.” The Central American nation joins a growing number of countries across Africa and the Americas that have signed contentious, often secretive agreements with the U.S. to accept deportees from other countries as U.S. President Donald Trump pressures governments to help him advance his agenda. In many cases, migrants who previously hoped to seek asylum in the U.S. are left in a legal “black hole” in...