Agreement is test for national detainer authority.More than a dozen Florida sheriffs announced a deal Wednesday that will allow them to hold illegal immigrants wanted by the federal government for deportation, in what’s likely to be a key test case for cities and countries eager to cooperate but worried about legal problems associated with helping the Trump administration. Known as the Basic Ordering Agreement, the deal struck between 17 Florida sheriffs and U.S. Immigration and Customs Enforcement would allow local authorities to hold illegal immigrants even beyond the time they normally would have to be released based on state or...