German authorities have detained an 18-year-old man after he allegedly discussed carrying out a knife attack on a synagogue in the south-western German city of Heidelberg. The suspect, who comes from the town of Weinheim, is being held on suspicion of conspiracy to commit murder, public prosecutors and criminal investigators in the south-western German state of Baden-Württemberg announced on Friday. He allegedly plotted the potential attack with another 24-year-old suspect, who was shot and captured by police earlier this month after a raid on the man’s flat turned violent. “The killing of one…