Add unique_id configuration option

[pilotak]

Description

This PR adds support for a configurable unique_id option for attribute sensors. Previously, the unique ID was automatically generated from the entity ID and device ID, but now users can specify a custom prefix.

Changes

• Added unique_id as an optional configuration parameter
• When provided, the unique_id is used as a prefix: {unique_id}_{entity_name}_{attribute}
• Falls back to the original auto-generated format if not specified (backward compatible)
• Uses CONF_UNIQUE_ID constant from homeassistant.const

Usage Example

sensor:
  - platform: attributes
    unique_id: "my_custom_prefix"
    attribute: battery_level
    entities:
      - sensor.myslipo_1_0
      - sensor.myslipo_2_0

This will create sensors with unique IDs like:

• my_custom_prefix_myslipo_1_0_battery_level
• my_custom_prefix_myslipo_2_0_battery_level

Backward Compatibility

✅ Fully backward compatible - existing configurations will continue to work without any changes.

[Tirpitz93]

created the attribute sensor for the versatile_bedroom but ID is still created as sensor.versatile_bedroom_temperature

[pilotak]

ok entity ID is not unique ID - that is a different thing. I will have to think about that