Remove device class timestamp from device condition and trigger

[MartinHjelmare]

Breaking change

• Remove unit of measurement from Garmin connect and system monitor timestamp sensors. It used to be set to empty string. Users should adjust automations and scripts that rely on unit of measurement for these sensors.

Proposed change

• Timestamp device class sensors don't have a unit of measurement. Device conditions and triggers will therefore not work with this sensor with our current way of creating device conditions and triggers, since they rely on a unit of measurement.
• Remove the timestamp device class from device conditions and triggers.
• Clean up a couple of integrations that had set a unit for device class timestamp incorrectly.
• The only remaining integration is subaru which currently also calculates state incorrectly for timestamp. This should be fixed separately.

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)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

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• This PR fixes or closes issue: fixes #
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[MartinHjelmare]

@bramkragten are there any changes needed for the frontend?

[probot-home-assistant]

Hey there @cyberjunky, mind taking a look at this pull request as its been labeled with an integration (garmin_connect) you are listed as a codeowner for? Thanks!
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[coryshack]

I do not notice any on the front end as of right now, looks good!

…

On Sun, Mar 28, 2021 at 8:19 AM Martin Hjelmare ***@***.***> wrote: @bramkragten <https://github.com/bramkragten> are there any changes needed for the frontend? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#48431 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ASR3YZQIYX6ZMCBEUI4SWXTTF4UFHANCNFSM4Z57JIPQ> .

[coryshack]

Made it into something treat is more simple when you could have gone the other way. On Sun, Mar 28, 2021 at 8:24 AM 4Cure Foundation ***@***.***> wrote:

…

I do not notice any on the front end as of right now, looks good! On Sun, Mar 28, 2021 at 8:19 AM Martin Hjelmare ***@***.***> wrote: > @bramkragten <https://github.com/bramkragten> are there any changes > needed for the frontend? > > — > You are receiving this because you are subscribed to this thread. > Reply to this email directly, view it on GitHub > <#48431 (comment)>, > or unsubscribe > <https://github.com/notifications/unsubscribe-auth/ASR3YZQIYX6ZMCBEUI4SWXTTF4UFHANCNFSM4Z57JIPQ> > . >

[MartinHjelmare]

Note that we don't change the icon, even though it should not be set when device class is set. I want to avoid a breaking change in this PR. We can fix this separately.

[MartinHjelmare]

Although technically setting the unit to None is also a breaking change.

[frenck]

Lets add a small note so it ends up in the release notes. Better to mention it, even if it is small. (which you did 👍 )

[bramkragten]

@bramkragten are there any changes needed for the frontend?

I don't think so