Fix Splunk HEC Event format

[Bre77]

Breaking change

The data format sent to Splunk has been corrected, you may need to update you searches in Splunk.

Proposed change

Correct the Splunk integrations JSON payload to conform to Splunk's HTTP Event Collector event endpoint. See https://docs.splunk.com/Documentation/SplunkCloud/latest/Data/FormateventsforHTTPEventCollector#Event_data

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

Example entry for configuration.yaml:

No changes from documentation, see https://www.home-assistant.io/integrations/splunk

Additional information

• This PR fixes the data format sent by the integration to match that of Splunk's documentation at https://docs.splunk.com/Documentation/Splunk/latest/Data/FormateventsforHTTPEventCollector#Event_data

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:

• No score or internal
• 🥈 Silver
• 🥇 Gold
• 🏆 Platinum

To help with the load of incoming pull requests:

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

[MartinHjelmare]

Unfortunately we can't accept changes to this integration until the interface code has been moved to a 3rd party library. Thanks for your contribution!

[MartinHjelmare]

Please extract the device specific interface code and data parsing to a standalone library published on PyPI.

https://developers.home-assistant.io/docs/creating_component_code_review#4-communication-with-devicesservices

[MartinHjelmare]

I'll close here now. If you want to do the refactor, please open a new PR. Thanks!