fix tests, refactor

common/cpp/include/asapo/database/database.h

common/cpp/include/asapo/unittests/MockDatabase.h

common/cpp/src/database/mongodb_client.cpp

common/cpp/src/database/mongodb_client.h

...ver/src/request_handler/request_handler_db_meta_write.cpp

...s/request_handler/test_request_handler_db_meta_writer.cpp

...atic/mongo_db/insert_retrieve/insert_retrieve_mongodb.cpp

tests/automatic/mongo_db/upsert/upsert_mongodb.cpp