Add OpenAI, Anthropic and Ollama providers

[davidmigloz]

This PR adds support for OpenAI, Anthropic and Ollama.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read the Flutter Style Guide recently, and have followed its advice.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

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[csells]

Hey, @davidmigloz. Instead of building the dependencies for these LLMs into the AI Toolkit, how about we build out another package specifically for these and potentially other community-provided LLM providers? Maybe call it flutter_ai_providers or flutter_ai_community_providers? I'm happy to work with you on it.

[davidmigloz]

Hey @csells,

That makes sense—it's the same approach we use in LangChain.dart. We have several "single provider" packages for the most popular ones (such as langchain_openai, langchain_anthropic, langchain_google, etc.) with minimal dependencies. But for other less popular providers, we use a generic langchain_community package.

Let me know how you'd like to proceed.

[csells]

My proposal: if you start up the repo with the structure for the package(s) you'd like to produce on pub.dev and add me as a contributor, then we can work together on them. Then we can publish them with your pub.dev publisher or mine.

I have a slight preference for a single package, at least to start. We can always split them up into others as needed.

Oh and I like flutter_ai_providers

[davidmigloz]

Sorry for the wait! @csells

I went ahead and created the repo (you should have received an invite) with the flutter_ai_providers package:

• https://github.com/davidmigloz/flutter_ai_community

I've integrated the 3 providers and added some simple tests. The package is not published yet. I'll wait for your feedback!

I'll close this PR.