Add GenericProvider

[qiuosier]

As part of ongoing enhancements, the OCI Generative AI Service is introducing additional models from xAI and OpenAI. These new models adhere to the same API specifications as the Meta models; however, the existing implementation does not automatically derive the associated provider for xAI or OpenAI models.

The MetaProvider provider can be used for xAI and OpenAI models provided by the OCI Generative AI service.
This PR fixes #13 by adding a simple change to automatically use MetaProvider when user is using xAI or OpenAI models.

[YouNeedCryDear]

1. I don't think OpenAI has been GA yet so we probably should remove it.
2. For xai, it is not appropriate to use the name MetaProvider. Instead, I think we should define a base class for GenericProvider for generic API type.
3. MetaProvider could be kept for backwards compatibility, but the implementation will likely be inheritance from GenericProvider.

[qiuosier]

Hi @YouNeedCryDear, thanks for the comment. I made the following updates:

1. Added a GenericProvider for both the llm model and the chat model.
2. Change the MetaProvider to inherit from GenericProvider.
3. Added _default_provider property.
4. For models with provider not found in the _provider_map, the _default_provider will be used.

Here is a screenshot of the test:@Property

[qiuosier]

I have updated the code to raise and error when customer endpoint is used without a provider.
The GenericProvider is used only if the model_id is not a custom endpoint.

[YouNeedCryDear]

The order might need to change. You have to check the self.model_id is None first, otherwise, this line will raise exception.

[qiuosier]

Sure. I moved up the logic to check if model_id is None.

BTW, is there a reason to allow model_id to be None?
It appears to me that the proper way to do model_id validation is not to allow None as default value in OCIGenAIBase. However, this is probably out of the scope here.

[YouNeedCryDear]

I think allowing model_id to be None was just an old langchain standard of how other vendor packages were doing. We sure can revisit the detail later.

[YouNeedCryDear]

I think allowing model_id to be None was just an old langchain standard of how other vendor packages were doing. We sure can revisit the detail later.