Rethink how products and producers are handled

[almet]

Currently, they're part of the delivery, but we might want to put them in a separate location, like it's done for groups, so that we don't have to copy them on every delivery.

If we do this, we might want to enable / disable them on a delivery basis.
Also, when we do this, we might want to keep a record of the prices and availability of the products, related to a delivery, but I'm not sure how we should handle this.

Ideas?

[indatwood]

Yeah, that's a good idea. We would need to rethink how stuff are handled in general if we want to have multiple collectives use the tool. So :

Here is a dependency thing :

- Collective : 
  - Groups
  - Deliveries
    - active producers
      - referents
    - orders
  - Producers
    - products
      - price

And we might even want to have multiple prices for the producers, in a way that would make the evolutoin of the prices traceable.