repo_management/cli.py:
Add `db2json()` which may serve as an entrypoint for a db2json script,
as it makes use of the argument parser defined in
`argparse.ArgParseFactory.db2json()` and calls
`operations.dump_db_to_json_files()` using the provided inputs.

tests/test_cli.py:
Add a unittest for `db2json()`, which patches all called methods.
The methods are tested extensively elsewhere. However, the function
should see proper integration testing via this endpoint in the future.