This change removes the infinite transmission loop with sleep periods
between each transmission. Now, a new transmission can start by a call
to "tx_start" on the following two conditions:
1) As soon as the application starts (if there is a previously paid
order waiting already).
2) As soon as the current transmission ends. The server will immediately
look for the next order ready for transmission and start it if
available.
Meanwhile, the condition for ending the current transmission (i.e., for
calling "tx_end(order)") is when all Tx confirmations are received from
all regions.
- 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/.
