Update docs for trigger-based template sensors. (#17243)

source/_integrations/template.markdown

@@ -25,7 +25,7 @@ ha_platforms:
 
 The `template` integration allows creating entities which derive their values from other entities. This is done by defining [templates](/docs/configuration/templating/) for each property of an entity, like the name or the state. Entities are updated automatically whenever a value that a template relies on changes.
 
-For sensors it's also possible to derive the state from [automation triggers](#configuration-for-trigger-based-template-sensors).
+For template sensors it's also possible to derive the state from [automation triggers](#configuration-for-trigger-based-template-sensors).
 
 Available template platforms:
 
@@ -152,6 +152,8 @@ curl --header "Content-Type: application/json" \
   http://homeassistant.local:8123/api/webhook/my-super-secret-webhook-id
 ```
 
+<p class='note'>Configuration under the <code>template:</code> key uses a different format compared to the platform configuration.</p>
+
 {% configuration %}
 trigger:
   description: The trigger configuration for this entity. [See trigger documentation](/docs/automation/trigger)
@@ -162,9 +164,54 @@ unique_id:
   required: false
   type: string
 sensor:
-  description: Map of your sensors to create from the trigger data. For available keys, see [configuration variables](#configuration-variables) above.
+  description: List of sensors to create from the trigger data.
   required: true
   type: map
+  keys:
+    state:
+      description: Defines a template to get the state of the sensor.
+      required: true
+      type: template
+    name:
+      description: Defines a template to get the name of the sensor.
+      required: false
+      type: template
+    unique_id:
+      description: An ID that uniquely identifies this sensor. Will be combined with the unique ID of the configuration block if available.
+      required: false
+      type: string
+    unit_of_measurement:
+      description: "Defines the units of measurement of the sensor, if any. This will also influence the graphical presentation in the history visualization as a continuous value. Sensors with missing `unit_of_measurement` are showing as discrete values."
+      required: false
+      type: string
+      default: None
+    icon:
+      description: Defines a template for the icon of the sensor.
+      required: false
+      type: template
+    picture:
+      description: Defines a template for the entity picture of the sensor.
+      required: false
+      type: template
+    attributes:
+      description: Defines templates for attributes of the sensor.
+      required: false
+      type: map
+      keys:
+        "attribute: template":
+          description: The attribute and corresponding template.
+          required: true
+          type: template
+    availability:
+      description: Defines a template to get the `available` state of the component. If the template returns `true`, the device is `available`. If the template returns any other value, the device will be `unavailable`. If not configured, the component will always be `available`.
+      required: false
+      type: template
+      default: true
+    device_class:
+      description: Sets the class of the device, changing the device state and icon that is displayed on the UI (see below). It does not set the `unit_of_measurement`.
+      required: false
+      type: device_class
+      default: None
 {% endconfiguration %}
 
 <p class='note'>It's currently only possible to define trigger-based entities via the top-level configuration. These entities are not yet included when reloading template entities.</p>