Added uuid import and clarification text

Author: LUS24

docs/docs/05_flask_smorest/02_data_model_improvements/README.md

@@ -245,6 +245,8 @@ def create_store():
 <TabItem value="new" label="create_store (new)">
 
 ```py title="app.py"
+import uuid
+
 @app.post("/store")
 def create_store():
     store_data = request.get_json()
@@ -255,6 +257,8 @@ def create_store():
     return store
 ```
 
+Here we add a new import, [the `uuid` module](https://docs.python.org/3/library/uuid.html). We will be using it to create unique IDs for our stores and items instead of relying on the uniqueness of their `names`.
+
 </TabItem>
 </Tabs>
 </div>