Add Model for version number and date, and util functions about billsim

[selama1]

Yes. This is all done. This is the currency table/currency_id we added.

[aih]

• We need to update pymodels to support version and date. We need a model (Currency) with three fields for now: id, date, version.

• In the BillToBill model, we need to add a foreign key field corresponding to the id of the Currency model.

[aih]

• Then, we will need to add functions to db_utils to save this update information each time we run the tool, and to include the id in any new bill-to-bill and section-to-section rows.

[aih]

This is similar to what is done with a temporal table, see Microsoft temporal tables

[aih]

• Once the db tables and utils are ready here, we will need to call them as part of the pipeline.

[aih]

@selama1 has this been done? Is it obsolete?