Options flow for Monoprice sources

[OnFreund]

Proposed change

Following up on the recent changes to the Monoprice integration, this PR enables the use of options flow to reconfigure sources.

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: Update doc with Monoprice options flow for source editing home-assistant.io#12500

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.
• Untested files have been added to .coveragerc.

The integration reached or maintains the following Integration Quality Scale:

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• 🏆 Platinum

[probot-home-assistant]

Hey there @etsinko, mind taking a look at this pull request as its been labeled with a integration (monoprice) you are listed as a codeowner for? Thanks!

[OnFreund]

@balloob @MartinHjelmare this is the options flow followup we discussed in #30337.

One problem I'm not sure how to resolve - since the options flow uses the Voluptuous default parameter to pre-fill the existing values, the only way to remove a value is to put a whitespace string (e.g. a single space) instead of it. Simply removing it keeps the old value in place.
Any idea how to resolve this?

Also, I think this integration is now a candidate for Gold on the quality scale. What do you think?

[balloob]

This looks ok. I don't have a solution for being able to remove an optional value. I know that we recently made a change for something similar in the frontend, but I can't recall nor find it, so I don't know if I am imagining it.

[OnFreund]

Thanks @balloob. Where would be a good place to open a ticket for the removal of an optional value, so that we're aware of the current limitation and hopefully find a solution in the future? Is that in the frontend repo or arch repo (since it's the backend that's currently controlling it)?

[balloob]

https://github.com/home-assistant/frontend. But it's difficult, because in most cases you do want the default :( So we would need a way to indicate allow_empty=True