[Suggestion] Add customer categories for drug preferences

[COVID-19]

In the roadmap[trello.com], one potential upcoming feature is visiting groups of travelling customers. These are categorized, e.g. a group of hippies will buy tonnes of weed or a group of businessmen will buy tonnes of cocaine, etc.

I think these drug-type preference categories should be applied to some existing customers too, to encourage and reward varied drug-type production.

I also think that customers' preferred effects should influence how much they are willing to pay per product, to encourage and reward varied effect production.