Fix no changelog API response

[mdegat01]

Proposed change

The status code of the changelog API when an addon had no changelog was accidently chnaged in #4972 . This PR changes it back to a 200 in this case and adds a unit test. It also fixes the /store/addons/{slug}/changelog API as it appears that hasn't worked for a long time (frontend is still using the supposedly deprecated /addons/{slug}/changelog and that did work).

As an aside this feels very hacky. We should simply return a 404 and the frontend should have the text to display in that case with localization. Supervisor should not be returning the message presented directly to users in this case.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (which adds functionality to the supervisor)
• 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 Supervisor JSON DECODE client error for add-ons without ChangeLog core#116470
• This PR is related to issue:
• Link to documentation pull request:
• Link to cli pull request:

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 Ruff (ruff format supervisor tests)
• Tests have been added to verify that the new code works.

If API endpoints of add-on configuration are added/changed:

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

[sairon]

Thanks, it's downfall of this change to be precise. I will take a look if it's the only place that relied on this rather weird handling but this PR fixes the issue, so 👍