Allow nested dictionary to be optional in addon config

[raman325]

Proposed change

See this issue for more details on the behavior I am trying to enable along with an example: #4606

I believe that if a nested dictionary is in the schema but not in the options and therefore hidden by default from the configuration UI, it should be optional, and I consider this a bug because you can hide it.

I know I need to refactor tests significantly for this change, but I wanted to get a sense of whether I am headed in the right direction before I continue.

I also attempted to improve the error message because I noticed that the key that failed validation is not always part of the message which makes it confusing.

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 Hidden nested dictionary in addon configuration causes validation to fail if dictionary isn't populated #4606
• 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 Black (black --fast 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

[pvizeli]

We should implement: #2640