docs: comparing sodas (#7890)

* docs: comparing sodas

* Update tutorial-dev-journey.md

* Update tutorial-dev-journey.md

docs/api/tutorial-dev-journey.md

@@ -16,7 +16,7 @@ To identify the potential users' needs, Dave has met with some conscious consume
 ### Developer journeys
 
 - []()Dev Journey 1: <a href="docs/reference/api-tutorials/comparing-sodas-for-anna.md">Comparing sodas for Anna</a>
-- []()Dev Journey 2: <a href="docs/reference/api-tutorials/finding-healthy-breakfast-cereals-for-stefano.md">Finding healthy breakfast cereals for Stefano</a>
+- []()Dev Journey 2: <a href="docs/reference/api-tutorials/finding-healthy-cereals.md">Finding healthy breakfast cereals for Stefano</a>
 - []()Dev Journey 3: <a href="docs/reference/api-tutorials/adding-missing-products.md">Adding missing products</a>
 - []()Dev Journey 4: <a href="docs/reference/api-tutorials/get-the-nutri-score.md">Get the Nutri-Score</a>
 - []()Dev Journey 5: <a href="docs/reference/api-tutorials/get-the-eco-score.md">Get the Eco-Score</a>

docs/reference/api-tutorials/comparing-sodas.md

@@ -0,0 +1,55 @@
+**Dave** wants his app to make an API call to provide Anna the information she needs to make a conscious choice when buying sodas.
+
+---
+
+#### Authentication and Header
+
+To make the API query that returns the products that might be interesting for Anna, Dave doesn't need to authenticate (`READ` request).
+
+However, he has to add a `User-Agent` HTTP Header with the name of his app, the version, system and a url (if any), so that he doesn't get blocked by mistake.
+
+In this case, that would be: `User-Agent: HealthyFoodChoices - Android - Version 1.0`
+
+---
+
+#### Subdomain
+
+Since Anna lives in NY, Dave wants to define the subdomain for the query as `us`. The subdomain automatically defines the country code (`cc`) and language of the interface (`lc`).
+
+The country code determines that only the products sold in the US are displayed. The language of the interface for the country code `us` is English.
+
+In this case:
+
+[https://us.openfoodfacts.org](https://us.openfoodfacts.org)
+
+---
+
+#### API Version
+
+The current version number of the Open Food Facts API is v0.
+
+[https://us.openfoodfacts.org/api/v0](https://us.openfoodfacts.org/api/v0)
+
+---
+
+#### Product Barcode
+
+After the version number, the word "product", followed by its barcode must be added:
+
+[https://us.openfoodfacts.org/api/v0/product/](https://us.openfoodfacts.org/api/v0/product/)
+
+The app will provide Anna with information about additives, sugars and nutriscore of different types of colas, to help her make her purchase decision.
+
+Anna selects the products she wants to compare in the application (Coca-Cola, Pepsi, Coca-Cola diet, Coca-Cola zero and Pepsi diet). The app retrieves the corresponding barcodes and makes the following calls:
+
+- Pepsico Pepsi Cola Soda:  
+    [https://us.openfoodfacts.org/api/v0/product/01223004](https://us.openfoodfacts.org/api/v0/product/01223004)
+- Coca-Cola Classic Coke Soft Drink  
+    [https://us.openfoodfacts.org/api/v0/product/04963406](https://us.openfoodfacts.org/api/v0/product/04963406)
+- Diet Pepsi  
+    [https://us.openfoodfacts.org/api/v0/product/069000019832](https://us.openfoodfacts.org/api/v0/product/069000019832)
+- Coca-Cola Zero  
+    [https://us.openfoodfacts.org/api/v0/product/5000112519945](https://us.openfoodfacts.org/api/v0/product/5000112519945)
+
+
+---