Support templated custom attributes for all template entities

[evercape]

Describe the enhancement

Summary
Extend the existing attributes: support available in template sensors and template binary_sensors to other template-based platforms, specifically:
• switch
• fan
• light
• climate

Current behavior
The template integration allows defining custom attributes for:
• sensor
• binary_sensor

Example (works today)

template:
  - sensor:
      - name: Example Sensor
        state: "{{ states('sensor.other') }}"
        attributes:
          source: "calculated"
          raw_value: "{{ states('sensor.other') }}"

However, the same attributes: key is ignored or unsupported when used with:
• template switches
• template fans
• template lights
• template climate entities

This forces users to create companion template sensors purely to hold metadata or derived attributes.

Example usage

Requested enhancement
Allow templated custom attributes to be defined directly on all template entity types, for example:


template:
  - fan:
      - name: Bathroom Fan
        state: "{{ is_state('switch.fan_relay', 'on') }}"
        attributes:
          room: "Master Bathroom"
          purpose: "Shower extraction"
          controlled_entity: "switch.fan_relay"

### Current workarounds

	•	customize.yaml (static only, not templatable)
	•	Companion template sensors (works, but adds unnecessary complexity)

### Anything else?

**Why this matters**
	1.	Consistency
	•	sensor and binary_sensor already support attributes.
	•	Other template entities behave inconsistently despite being part of the same integration.
	2.	Cleaner configurations
	•	Avoids “metadata-only” helper sensors.
	•	Reduces entity sprawl and recorder load.
	3.	Improved automation & UI logic
	•	Attributes are frequently used for:
	•	UI secondary info
	•	Dynamic dashboards
	•	Generic automations
	•	Blueprints
	•	Having attributes on the primary entity is more intuitive and maintainable.
	4.	Precedent exists
	•	Community components (e.g. hass-template-climate) already demonstrate attribute templating successfully.
	•	Core already handles attribute rendering for template entities internally.

**Scope / expectations**
	•	No behavioral changes to entity state logic
	•	Attribute rendering would follow the same model as template sensors:
	•	Jinja templates
	•	Static or dynamic values
	•	Updated on entity refresh
	•	Backwards-compatible

[evercape]

@Petro31 could you maybe have a look at this please, seeing that you worked on binary_sensor before?

[oerix]

This would be a very valuable addition, instead on relying on yaml.

[Petro31]

If this was added, it would be yaml only.

[oerix]

Whoop, I meant as oppose to the current way without the Helper UI.

[evercape]

thanks - this would be awesome to have this added via yaml.

[evercape]

Happy to test

[Petro31]

PR here

home-assistant/core#178762