Allow string values for foriegn_key from other modules

[knyghty]

It would be nice if we could treat foreign keys like we would a recipe in baker.make(). Right now it seems like whatever foreign key you use has to be imported into that baker_recipes.py file.

Expected behavior

It would be nice to be able to do something like:

order = Recipe(account=foreign_key('accounts.account'))

It would be even nicer if this would handle things gracefully, if you had for example one recipe that creates an order tied to an account, and a recipe that creates an account with several orders, both in different baker_recipes.py files.

Actual behavior

I get an error in the form of:

AttributeError: module 'order.baker_recipes' has no attribute 'account.account'

Reproduction Steps

Create two baker_recipes.py files in different django apps/whatever and try to use them together without importing recipes from the other.

Versions

Python: 3.7
Django: 2.2
Model Bakery: 1.0.2