Added database driver selector.

cookiecutter.json

{{cookiecutter.project_name}}/pyproject.toml

{{cookiecutter.project_name}}/scheduler.py

{{cookiecutter.project_name}}/src/api/dummy_db/schema.py

{{cookiecutter.project_name}}/src/models/dummy_db_model.py

{{cookiecutter.project_name}}/src/server.py

{{cookiecutter.project_name}}/src/services/db.py