Move from a direct access to DB by the parsers/categorizers to a middle
layer, which will bring an easier way to have two input alternatives.
This patch starts by instantiating the manager on the cli runnable and
using it for the parser function.
This patch also moves the queries to a different file, so that
introducing new functions on the DB client becomes more manageable and
clearer.
Finally, the new manager will need converters to move from the code type
Transaction to the DB types. This will eventually simplify the code data
model by removing more of its method and leaving it a simple dataclass.
Issue #14
