Add a line return after closing parenthesis in DKIM.

src/storage/zone.cr

@@ -508,14 +508,14 @@ class DNSManager::Storage::Zone
 			io << "#{ "%30s" % @name} #{ "%6d" % @ttl} DKIM "
 			io << "( "
 			io << split_line dkim.to_s
-			io << " )"
+			io << " )\n"
 		end
 
 		def to_bind9(io : IO)
 			io << "#{@name} #{@ttl} IN TXT "
 			io << "( "
 			io << split_line dkim.to_s
-			io << " )"
+			io << " )\n"
 		end
 	end