[PACKS] #0 Add fields for packs to the model

[cielf]

Summary

Add fields for packs to the model, plus some sample seed data

Why?

We're intending to do packs at the RFG event. Having the fields in place on the model first will allow us to get a lot more done than otherwise.

Details

We need to model:
1/ A flag on Organization to indicate the org uses custom request units
2/ Custom reporting units used by the organization
3/ Selection of custom reporting units used on an item level. Reporting unit, plus other units allowed.
4/ What custom reporting unit is used on a request

As far as seed data goes, we should have packs enabled on the the bank that org_admin1 signs in to, with "diapers", "packs", "pads" and "flats" as the units the org uses.
Have a three items in the seed that have custom units, one that allows "diapers" and "packs", one that allows "diapers", "packs" and "flats". Both of these will have "diapers" as the reporting unit.
A third item (preferably "Pads", to keep the data nice for demo purposes) will have "pads" as its reporting unit, with "packs" as another option.

At this time, this is a model with no UI. There are issues to follow for all the UI components, which will be addressed at this year's event.

From the planning meeting

We need an "Organization_Request_Units" table
And an "Item_Request_Units" table

Criteria for completion

• model changes made (models and tables are created)
• seed data works
• any tests that are useful at this point. (validation - can't add an item unit unless there is an org unit)

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