Change u'id' from unicode to ascii string
Created a test for the product model

refs #16431
Use ForeignKey for foreign keys and NullBooleanField in tests
Create Product model
Changed link field from TextField to URLField

refs #16431
Merge branch 'feature/16431' of github.com:osu-cass/whats-fresh-api into feature/16431

Conflicts:
	project_fish/whats_fresh/tests/test_products_model.py
Updated link field from TextField to URL field

refs #16431

Updated the link field in the product model to match the test.
Change id field unicode string to ascii string
Begin vendor/product model join tests
Add proper tests for vendor and product models for their relationship
Merge branch 'feature/16455' of https://github.com/osu-cass/whats-fresh-api into feature/16455