Add template filter timedelta

[jschlyter]

Proposed change

Add template filter timedelta to create a timedelta object from seconds. This can be used when sensors report a duration and can be converted into readable text when combined with relative_time(), e.g.:

{{ relative_time(now() - timedelta(seconds=3600)) }}

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

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request: add timedelta_seconds() home-assistant.io#14384

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
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• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

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[bdraco]

Can we accept all the units of time that time delta supports instead of creating a function that only works with seconds?

[balloob]

@bdraco you mean just exposing timedelta ?

[bdraco]

@bdraco you mean just exposing timedelta ?

Yes

[jschlyter]

@bdraco you mean just exposing timedelta ?

Yes

I'm happy to add all the timedelta kwargs if that's what we want.

[bdraco]

@bdraco you mean just exposing timedelta ?

Yes

I'm happy to add all the timedelta kwargs if that's what we want.

That seems the most future proof so we don't end up with a timedeta_minutes etc

[jschlyter]

Based on comments from @bdraco I've change the code (but not yet the docs) to expose a raw datetime.timedelta.

[balloob]

Can be merged once docs updated 👍

[basnijholt]

Might be a good idea to change the name of the PR to

Add template filter timedelta

because the title isn't correct anymore and the release notes use the title (IIUC).