Add support for color_temp_command_template in MQTT light component

[dchesterton]

Description:

Add support for changing the MQTT color_temp command with the color_temp_command_template config option, in the same way as the existing rgb_command_template config option. This adds support for devices which expect the color_temp to be in Kelvin, such as SmartThings and Hubitat.

Related issue (if applicable): fixes #19673 (among others)

Pull request in home-assistant.io with documentation (if applicable): home-assistant/home-assistant.io#8000

Example entry for configuration.yaml (if applicable):

light:
  - platform: mqtt
    color_temp_command_topic: "devices/bulb/color_temp"
    color_temp_command_template: "{{ (1000 / value) | round(0) }}"

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.io

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[homeassistant]

Hi @dchesterton,

It seems you haven't yet signed a CLA. Please do so here.

Once you do that we will be able to review and accept this pull request.

Thanks!

[houndci-bot]

line too long (91 > 79 characters)

[emontnemery]

Please add an abbreviation for the new configuration variable in mqtt/discovery.py

[dchesterton]

Thanks, I've added the abbreviation.

[emontnemery]

Looks good.