feat: Conversion of Anthropic Extension to M.E.AI interface [WIP]

[lokitoth]

Why are these changes needed?

Enables use of multiple backends (as in 0.2) with 0.4 using the Microsoft.Extensions.AI interfaces.

Related issue number

Progress for #3919

Remaining to be done

• AutoGen.Anthropic
• AutoGen.Gemini
• AutoGen.Mistral
• AutoGen.WebAPI
• AutoGen.DotnetInteractive (depends on AgentChat PR, coming soon)

Unclear if still needed with the M.E.AI.AIFunction

• AutoGen.SourceGenerator?

These got done via MEAI hosting in Microsoft.AutoGen.Extensions.MEAI

• AutoGen.Ollama
• AutoGen.OpenAI
• AutoGen.AzureAIInference

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[LittleLittleCloud]

I feel like this PR can benefit much more .NET developers if moving to M.E.AI library, what you think

[LittleLittleCloud]

Just a suggestion that there's a library called AutoSDK which allows you to generate the client library from openapi.yaml. That might worth a try if you don't want to manually port the DTO classes.

• https://github.com/tryAGI/AutoSDK

[lokitoth]

Ah, I just moved them over the AutoGen.Anthropic project so we can reuse the same code. Happy to rebuild the inner client on top of AutoSDK, if you think it is worth it?

[LittleLittleCloud]

Yes I think we can look into that option (or any options that enables generating OpenAPI client from schema, looks like there are quite a few of them Wondering how many of these options support polymorphism) after this PR. It's really attractive to me to not necessarily writing contract/DTO code by hand)

[lokitoth]

I feel like this PR can benefit much more .NET developers if moving to M.E.AI library, what you think

Agreed; the point of Microsoft.Autogen.Extensions.Anthropic is to provide an IChatClient implementation of the Anthropic APIs until there is an official variant. The only reason we keep the old infrastructure is that I did not want to rebuild everything by hand and have two copies.