Add Downloader config flow, including tests

[erwindouna]

Breaking change

Proposed change

The scope is to create a proper config flow for the Downloader integration. Parts have been recoded so they integrate better with the async_setup_entry and registering services. It also includes a unit test for the conflig flow, plus an extra validation to check if the folder exsists in the config flow.

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)
• [x] Deprecation (breaking change to happen in the future)
• [ ] Breaking change (fix/feature causing existing functionality to break)
• [x] 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:

Checklist

• [x] The code change is tested and works locally.
• [x] Local tests pass. Your PR cannot be merged unless tests pass
• [x] There is no commented out code in this PR.
• [x] I have followed the development checklist
• [x] I have followed the perfect PR recommendations
• [x] The code has been formatted using Black (black --fast homeassistant tests)
• [x] 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.

To help with the load of incoming pull requests:

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

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[emontnemery]

Please mark the PR ready for review when all changes which are not needed for setting up downloader from a config entry have been reverted.

[erwindouna]

Again, please remove all the unrelated changes. To be clear, I'm talking about changes like these which have nothing to do with the config entry change:

Thanks for clarifying. I reverted back the parts.

[frenck]

@erwindouna @emontnemery Could be me, but is this PR missing a documentation PR?

[erwindouna]

@erwindouna @emontnemery Could be me, but is this PR missing a documentation PR?

You're right - thanks for pointing out. I will create a documentation PR this evening to align with this PR. :)

[frenck]

Thanks, @erwindouna 👍