Add ppb to allowed VOC values

[elupus]

Proposed change

Allow PPB as VOC unit.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes homeassistant.components.zha.sensor.PPBVOCLevel invalid native unit of measurement 'ppb' #85726 Airthings BLE using invalid unit of measuremen for VOC entity #85293
• Docs: Add ppb to voc home-assistant.io#25770
• Arch: Add ppb to volatile_organic_compounds architecture#858

Checklist

• The code change is tested and works locally.
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• Tests have been added to verify that the new code works.

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[home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as it has been labeled with an integration (sensor) you are listed as a code owner for? Thanks!

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[frenck]

Additions of units has been flowing through the architecture repository. Please create an discussion there and provide an overview of the use.

Thanks 👍

../Frenck

[epenet]

I'm not against it, but needs adjustments in:

• SensorDeviceClass docstring
• NumberDeviceClass docstring
• dev docs
• user docs

I also suggest that you look for original arch discussion around the device class to see if there was a reason to exclude.

[frenck]

Removed the milestone as per above.

[zsawyer]

ppb is parts per billion, not million. Is this intentional?

[elupus]

Not really. But this pull is going no where. A new device class needs to be added.