Add basic main file

from pathlib import Path

from sqlalchemy import create_engine

from sqlalchemy.orm import Session

from poolpay import db

from poolpay.model.Retrievable import Retrievable

proj_dir = Path(__file__).parent.parent.resolve()

instance_dir = proj_dir / "instance"

db_file = instance_dir / "poolpay.db"

try:

    engine = create_engine(f"sqlite:///{db_file}")

    Retrievable.metadata.create_all(engine)

    db.session = Session(engine)