injest mode for producer

common/cpp/include/common/networking.h

producer/api/include/producer/producer_error.h

producer/api/src/producer_impl.cpp

producer/api/src/producer_impl.h

producer/api/src/request_handler_tcp.cpp

producer/api/unittests/test_producer_impl.cpp

producer/api/unittests/test_request_handler_tcp.cpp

receiver/src/request_handler_db_write.cpp

receiver/unittests/test_request_handler_db_writer.cpp