Document use cases

This is a Gold rule. In quality_scale.yaml, it is called docs-use-cases.

The integration page on home-assistant.io describes a few use cases: what you can do with the device or service once it is in Home Assistant, and why you would want it there.

For some integrations, the value is obvious: a smart light is for turning on the light. For others, a user looks at the integration and wonders why they would bother. A few concrete use cases answer that question, and often give people ideas they would not have had themselves.

Use cases are about the why. docs-examples is about the how, with automations to copy.

## Use cases

The water meter of My Company reports your water usage every minute.
In Home Assistant, you can:

- Track your water usage in the energy dashboard, next to electricity
  and gas.
- Get a notification when water keeps running for an hour, which often
  means a leak or a running toilet.
- Compare your usage per day, to see what the garden sprinklers cost.

See Write integration documentation and the integration page structure for where this section goes.

Checked in review, usually on the documentation pull request.

There are no exceptions to this rule.