Add update entity platform

[frenck]

Proposed change

This PR adds a new entity platform to Home Assistant: update.
Based on the original work by @ludeeus in #66552, but this time as an entity platform.

A screen recorder from earlier in the development process, to give an idea of what this entity can do (will update with a new one, once I finish the demo integration part)

The next step is to adjust the frontend to handle this entity and show pending updates in the configuration screen.

TODO:

• Finish Demo integration implementation
• Developer documentation PR
• End-user documentation PR

Future steps:

• Frontend
  • Entity row support
  • More info dialog support
  • Show updates in config dashboard
• Add support to Google Assistant
• Add support to Alexa
• Add support to HomeKit
• Add support to MQTT
• Device trigger/condition/action support

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 update entity platform home-assistant.io#22082
• Link to developer documentation pull request: Add update entity platform developers.home-assistant#1243

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• 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

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.
• Untested files have been added to .coveragerc.

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To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[gwww]

Cool new feature!

[gwww]

Can the UpdateEntity be used to downgrade versions?

[frenck]

Can the UpdateEntity be used to downgrade versions?

That is up to the implementer of the platform.

[ludeeus]

LGTM 🎉

[balloob]

Should update in progress also be a state? I guess it depends on what the update entity describes. If it describes the availability of an update, on/off seems fine. If it describes an update, maybe ready/applying/on_latest would fit better? After all, that is also what the entity row would show

[frenck]

Good question, and initially I wrote it as such as well. I kept it binary and simple. The progress moved to an attribute.

My train of though here was three fold:

• it still isn't updated while updating.
• the current form allows for translations in the frontend.
• the main use case of the entity state would be dermining if there is an update pending (and automate notification on that). Less possible states makes that easier I guess.

[balloob]

Ok 👍 It means we think of it as representing version.

[frenck]

Updates:

• Rebased to deal with a merge conflict in .core-files.yaml
• Processed review comments
• PR now depends on and awaits Raise if referenced entity does not support service #68394

For the latter, I'll mark this PR as a draft as it needs to be rebased once #68394 is merged.

[frenck]

Rebased onto the latest dev, now #68394 is merged.