refactored signup flow for entire registration process. Utilized seed data option for optional seeding of Foods, Units, and Labels. Localized registration page.
* Added validators for users and recipes
provide a simple get api, allowing to test for existence of
- user by username
- recipe by slug
- group by name (not tested yet)
* updated formatting
* Use group_id+slug for recipes, use ValidationRespone
* Fixed Flake8 errors and warnings
* add missing field for TestUser init