This change implements a mechanism to retransmit orders if some of the
order's selected regions do not confirm transmission in due time. It
adds a worker to repeatedly check the orders and determine if they need
retransmission. Such orders will be added to a new table named
tx_retries. The tx_start function now first checks if there are regular
new paid orders to transmit. If not, it will check the retransmission
table and retransmit an order from there if one is available.
This patch also introduces a new order state called "retranmission". The
order enters this state while waiting for retransmission.
- Preserve the SQLite database and use SQLAlchemy to wrap db
interactions.
- Use Alembic for database migrations.
- Organize all the python modules on the new server/ directory.
- Use pytest for unit tests and organize test modules at server/tests/.
