docs: update generator-template.md for AsyncAPI v3 parser usage

apps/generator/docs/generator-template.md

@@ -39,44 +39,51 @@ Before you begin, make sure you have the following set up:
 
 ## Background context
 
-There is a list of [community maintained templates](https://www.asyncapi.com/docs/tools/generator/template#generator-templates-list), but what if you do not find what you need? In that case, you'll create a user-defined template that generates custom output from the generator.
-Before you create the template, you'll need to have an [AsyncAPI document](https://www.asyncapi.com/docs/tools/generator/asyncapi-document) that defines the properties you want to use in your template to test against. In this tutorial, you'll use the following template saved in the **test/fixtures/asyncapi.yml** file in your template project directory.
+**This tutorial focuses on code generation using templates — not full AsyncAPI document modeling.**
 
-``` yml
+There is a list of [community maintained templates](https://www.asyncapi.com/docs/tools/generator/template#generator-templates-list), but what if you do not find what you need? In that case, you'll create a user-defined template that generates custom output from the generator.
+Before you create the template, you'll need an [AsyncAPI document](https://www.asyncapi.com/docs/tools/generator/asyncapi-document) that defines the properties used in your generator.
+In this tutorial, we use a simplified AsyncAPI document focused on extracting data for template generation.
+You'll use the following document saved as test/fixtures/asyncapi.yml.
 
-asyncapi: 2.6.0
 
+```yaml
+asyncapi: "3.0.0"
 info:
   title: Temperature Service
   version: 1.0.0
-  description: This service is in charge of processing all the events related to temperature.
+  description: Service that emits temperature changes from a bedroom sensor.
 
 servers:
   dev:
     url: test.mosquitto.org #in case you're using local mosquitto instance, change this value to localhost.
     protocol: mqtt
 
 channels:
-  temperature/changed:
-    description: Updates the bedroom temperature in the database when the temperatures drops or goes up.
-    publish:
-      operationId: temperatureChange
-      message:
-        description: Message that is being sent when the temperature in the bedroom changes.
+  temperatureChanged:
+    address: temperature/changed
+    messages:
+      temperatureChange:
+        description: Message sent when the temperature in the bedroom changes.
         payload:
-          type: object
-          additionalProperties: false
-          properties:
-            temperatureId:
-              type: string
+          $ref: '#/components/schemas/Temperature' # refactored from inline payload for better reuse
+
+operations:
+  sendTemperatureChanged:
+    action: send
+    summary: Temperature changes are pushed to the broker
+    channel:
+      $ref: '#/channels/temperatureChanged'
+
 components:
   schemas:
-    temperatureId:
+    Temperature:
       type: object
       additionalProperties: false
       properties:
         temperatureId:
           type: string
+
 ```
 
 ## Overview of steps
@@ -100,7 +107,7 @@ python-mqtt-client-template
 └── package.json
 ```
 
-Lets break it down:
+Let's break it down:
 
 ### package.json file
 
@@ -649,4 +656,4 @@ Great job completing this tutorial! You have learnt how to use an AsyncAPI file
 
 If you want to tinker with a completed template and see what it would look like in production, check out the [Paho-MQTT template](https://github.com/derberg/python-mqtt-client-template/tree/v1.0.0). You can also check out the accompanying [article about creating MQTT client code](https://www.brainfart.dev/blog/asyncapi-codegen-python).
 
-You can also check out the [MQTT beginners guide](https://medium.com/python-point/mqtt-basics-with-python-examples-7c758e605d4) tutorial to learn more about asynchronous messaging using MQTT.
+You can also check out the [MQTT beginners guide](https://medium.com/python-point/mqtt-basics-with-python-examples-7c758e605d4) tutorial to learn more about asynchronous messaging using MQTT.