Move manual configuration of MQTT fan and light to the integration key

[jbouwh]

Breaking change

Defining manually configured MQTT entities directly under the respective platform keys (e.g. fan, light) is deprecated and support will be removed in Home Assistant Core 2022.9.
Manually configured MQTT entities should now be defined under the mqtt key in configuration.yaml instead of under the platform key.

As an example, this is now deprecated:

sensor:
  - platform: "mqtt"
    name: "My sensor"
    state_topic: "some-state-topic"

The configuration needs to updated to this format:

mqtt:
  sensor:
   - name: "My sensor"
     state_topic: "some-state-topic"

Proposed change

Setup MQTT yaml configured entities through config entry setup.
The PR will deprecate setting up MQTT entities using the following form:

sensor:
  - platform: "mqtt"
    name: "My sensor"
    state_topic: "some-state-topic"

New manual configured MQTT entities need to be setup in the following form:

mqtt:
  sensor:
   - name: "My sensor"
     state_topic: "some-state-topic"

The platform schema will stay the same, but the platform configuration item should not be configured.

The current PR (PoC) implements the platforms:

• light
• fan

A single test test_setup_manual_entity_from_yaml is added for each platform. A helper help_test_setup_manual_entity_from_yaml is added to make it easy to add a tests for the additional platform.

TODO (in follow-up PRs):

• Convert all tests to mainly test manual added MQTT items using the integration key.
• Implement the other platforms (will be done with different PR's).

The background for this PR is that the MQTT integration itself is setup via a config entry, with entities setup via discovery.
MQTT entities can also be setup through configuration.yaml though, and those entities are not aware of the MQTT config entry and thus are not removed if the MQTT config entry is disabled or removed.

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: MQTT Manual config items under integration key Fan and Light platform home-assistant.io#22805

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

[probot-home-assistant]

Hey there @emontnemery, mind taking a look at this pull request as it has been labeled with an integration (mqtt) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[emontnemery]

I think this is a good change, I'd like a 2nd opinion though just in case I miss something.

[MartinHjelmare]

We'll have time to move all platforms before beta cut next week?

[jbouwh]

We'll have time to move all platforms before beta cut next week?

Sure. As soon as this is merged i'll submit PR's for all remaining platforms. There are already prepared :-)

[frenck]

Nice work @jbouwh 👍 Tested locally and works as expected.
I'm not sure about the documentation URL yet to be honest, but we can change that later if needed 👍

[frenck]

Oh, merged. Alright that's good too I guess 😞