State_class: "measurement" for platform: template

Use the new modern template sensor format-

Your new template sensor should look like-

template:
  - sensor:
      - name: "EndesaOK Utility Meter"
        unit_of_measurement: "kWh"
        device_class: energy
        state_class: measurement
        state: >-
          {{ state_attr('sensor.endesa_energy', 'energy') /1000*400 }}

Note: Legacy template sensor format does not support measurement state_class.

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