docs: Added automation example for calendars

Author: BottlecapDave

_docs/entities/octoplus.md

@@ -53,6 +53,26 @@ Calendar sensor to record saving sessions. Will be `on` when a saving session th
 
     The events are supplied by OE API and does not store past events indefinitely. Past events could be removed without notice.
 
+### Automation Example
+
+Below is an example of raising a persistent notification 5 minutes before a saving session starts.
+
+```yaml
+triggers:
+- trigger: calendar
+  entity_id: calendar.octopus_energy_{{ACCOUNT_ID}}_octoplus_saving_sessions
+  event: start
+  offset: -00:05:00
+actions:
+- action: persistent_notification.create
+  data:
+    title: Saving Session Starting
+    message: >
+      {% set minutes = ((state_attr(trigger.entity_id, 'end_time') | as_datetime - state_attr(trigger.entity_id, 'start_time') | as_datetime).seconds / 60) | round(0) | string %}
+      {% set start_time = (state_attr(trigger.entity_id, 'start_time') | as_datetime).strftime('%H:%M') %}
+      Saving session starts at {{ start_time }} for {{ minutes }} minutes.
+```
+
 ## Saving Session Events
 
 `event.octopus_energy_{{ACCOUNT_ID}}_octoplus_saving_session_events`
@@ -182,6 +202,26 @@ Calendar sensor to record free electricity sessions. Will be `on` when a free el
 
     You can use the [data_last_retrieved sensor](./diagnostics.md#free-electricity-sessions-data-last-retrieved) to determine when the underlying data was last retrieved from the OE servers.
 
+### Automation Example
+
+Below is an example of raising a persistent notification 5 minutes before a free electricity session starts.
+
+```yaml
+triggers:
+- trigger: calendar
+  entity_id: calendar.octopus_energy_{{ACCOUNT_ID}}_octoplus_free_electricity_session
+  event: start
+  offset: -00:05:00
+actions:
+- action: persistent_notification.create
+  data:
+    title: Free Electricity Session Starting
+    message: >
+      {% set minutes = ((state_attr(trigger.entity_id, 'end_time') | as_datetime - state_attr(trigger.entity_id, 'start_time') | as_datetime).seconds / 60) | round(0) | string %}
+      {% set start_time = (state_attr(trigger.entity_id, 'start_time') | as_datetime).strftime('%H:%M') %}
+      Free electricity session starts at {{ start_time }} for {{ minutes }} minutes.
+```
+
 ## Free Electricity Session Events
 
 `event.octopus_energy_{{ACCOUNT_ID}}_octoplus_free_electricity_session_events`