This commit introduces a new partial to display nutritional data from the Australian Food Composition Database.
Key changes:
- Adds a database index to the `public_food_key` on the `crops` table.
- Establishes a `has_one` relationship between `Crop` and `AustralianFoodClassificationData`.
- Creates a `_nutritional_data.html.haml` partial to display a summary of key nutritional information.
- Renders the partial on the `show` pages for both crops and harvests.