Allow custom service name for dropdowns

[htmltiger]

This will allow water level settings for Xiaomi Vacuum 1C STYTJ01ZHM (dreame.vacuum.mc1808) with the help of https://github.com/Concentricc/xiaomi_vacuum

state:
  water:
    key: water_level
    icon: 'mdi:water-percent'
    service: xiaomi_vacuum.set_water_level

[benct]

Thanks!