Add generate content service for OpenAI to match Google AI

[timlaing]

Proposed change

Extended the OpenAI Conversation integration such that it contains an equivalent generate_content service as the Google AI integration. This allows for feature parity between these two integrations. This is important for countries that the Free tier of Google AI is not provided.

Type of change

• [ ] Dependency upgrade
• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New integration (thank you!)
• [X] New feature (which adds functionality to an existing integration)
• [ ] Deprecation (breaking change to happen in the future)
• [ ] 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: https://github.com/home-assistant/home-assistant.io/pull/34072

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 Ruff (ruff format homeassistant tests)
• [X] Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• [X] 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.

To help with the load of incoming pull requests:

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

[home-assistant[bot]]

Hey there @balloob, mind taking a look at this pull request as it has been labeled with an integration (openai_conversation) you are listed as a code owner for? Thanks!

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[timlaing]

I have updated the code to fix the issues from the code checks. Also rebased against latest dev.

[home-assistant[bot]]

Please take a look at the requested changes, and use the Ready for review button when you are done, thanks :+1:

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[github-actions[bot]]

There hasn't been any activity on this pull request recently. This pull request has been automatically marked as stale because of that and will be closed if no further activity occurs within 7 days. If you are the author of this PR, please leave a comment if you want to keep it open. Also, please rebase your PR onto the latest dev branch to ensure that it's up to date with the latest changes. Thank you for your contribution!

[timlaing]

I believe I have addressed all of your comments.

[timlaing]

Left some comments that need addressing.

Thanks for the feedback - these comments have been addressed.

[timlaing]

Some more changes requested.

Thanks again for your comments. I believe that these have been addressed correctly.

[balloob]

Sorry for the long delay and thank you for patience. Approved! 🐬 ✅

[timlaing]

Sorry for the long delay and thank you for patience. Approved! 🐬 ✅

Not a problem thank you too.