Add template extension coordinates

[eifinger]

Description:

This template extension will allow for a clean and reusable way to enable dynamic travel_time sensors. The issue was discussed several times in the forum here and here as well as in the PRs #27237 #28716.

Using this template the following config is possible:

input_select:
  here_destination_preset:
    options:
      - zone.home
      - zone.office
      - zone.somewheredefault

sensor:
  - platform: here_travel_time
    api_key: my_api_key
    name: Reistijd
    origin_template: {{ coordinates('device_tracker.myphone') }}
    destination_template: {{ coordinates('input_select.here_destination_preset') }}

automation:    
  - alias: 'set'
    trigger:
      - platform: homeassistant
        event: start
      - platform: time
        at: 00:00
    action:
       service: input_select.select_option
       data_template:
        entity_id: input_select.here_destination_preset
        option: "{% if is_state('device_tracker.myphone','home') %}zone.office{% elif is_state('device_tracker.myphone','office') %}zone.home{% else %}zone.somewheredefault{% endif %}"

The simple case {{ coordinates('device_tracker.myphone') }} can already be accomplished with existing methods but now the user does not have to know that a device_tracker stores latitude and longitude as attributes.

The nested case {{ coordinates('input_select.here_destination_preset') }} is currently only possible by creating a complex structure of dependent template_sensors using complex templates.

Pull request in home-assistant (if applicable): home-assistant/core#30019

Checklist:

• Branch: next is for changes and new documentation that will go public with the next Home Assistant release. Fixes, changes and adjustments for the current release should be created against current.
• The documentation follows the standards.

[frenck]

✅ Approved. Can be merged as soon as the parent PR gets merged.