Add missing header

test/test_transaction.cpp

@@ -22,6 +22,7 @@
 #include "caosdb/connection.h"                    // for Connection, Connec...
 #include "caosdb/data_type.h"                     // for AtomicDataType
 #include "caosdb/entity.h"                        // for Entity, Property
+#include "caosdb/file_descriptor.h"               // for FileDescriptor
 #include "caosdb/file_transmission/file_reader.h" // for path, FileReader
 #include "caosdb/file_transmission/file_writer.h" // for FileWriter
 #include "caosdb/message_code.h"                  // for MessageCode, ENTIT...