Trying to cast local media

Configuration
1

What am I doing wrong here?

  - alias: "Back Door Open"
    trigger:
      - platform: state
        entity_id: binary_sensor.back_door
        to: 'on'
    action:
      - service: media_player.play_media
        data_template:
          entity_id: media_player.master_speaker
          media_content_id: 'https://10.0.0.115:8123/local/audio/backdoor.mp3'
          media_content_type: 'audio/mp3'
2

https?, do you get any errors in the log?

3

data: instead of data_template: ??