Add documentation for scripts and service calls with response data (#27863)

Co-authored-by: c0ffeeca7 <38767475+c0ffeeca7@users.noreply.github.com>
Co-authored-by: Franck Nijhof <frenck@frenck.nl>

source/_docs/scripts/service-calls.markdown

@@ -125,6 +125,57 @@ data: >
 
 {% endraw %}
 
+### Use templates to handle response data
+
+Some services may respond with data that can be used in automation. This data is called _service response data_. Service response data
+is typically used for data that is dynamic or large and which may not be suited for use in entity state.
+Examples of service response data are upcoming calendar events for the next week or detailed driving directions.
+
+Templates can also be used for handling response data. The service call can specify
+a `response_variable`. This is the [variable](/docs/scripts/#variables)
+that contains the response data. You can define any name for your `response_variable`. This example calls a service and stores the response in 
+the variable called `agenda`.
+
+{% raw %}
+
+```yaml
+service: calendar.list_events
+target:
+  entity_id: calendar.school
+data:
+  duration:
+    hours: 24
+response_variable: agenda
+```
+
+{% endraw %}
+
+You may then use the response data in the variable `agenda` in another action
+in the same script. The example below sends a notification using the response
+data.
+
+<div class='note'>
+Which data fields can be used in a service call depends on the type of notification service that is used.
+</div>
+
+{% raw %}
+
+```yaml
+service: notify.gmail_com
+data:
+  target: "gduser1@workspacesamples.dev"
+  title: "Daily agenda for {{ now().date() }}"
+  message: >-
+    Your agenda for today:
+    <p>
+    {% for event in agenda.events %}
+    {{ event.start}}: {{ event.summary }}<br>
+    {% endfor %}
+    </p>
+```
+
+{% endraw %}
+
 ### `homeassistant` services
 
 There are four `homeassistant` services that aren't tied to any single domain, these are: