feat(backend): adding Azure AI Foundry OpenAPI support

[Sma1lboy]

Azure OpenAI HTTP API Support

Added HTTP API support for Azure OpenAI Service, enabling seamless integration with all OpenAI API models available through Azure AI Service, including:

• GPT series chat models
• Embedding models

add the following configuration to your ~/.tabby/config.toml to get started:

# Configure chat model
[model.chat.http]
kind = "azure/chat"
model_name = "gpt-4o-mini"
api_endpoint = "https://xxx.openai.azure.com"  
api_key = "your-api-key"

# Configure embedding model
[model.embedding.http]
kind = "azure/embedding"
model_name = "text-embedding-3-small"
api_endpoint = "https://xxx.openai.azure.com"  
api_key = "your-api-key"

Relate Issues

• Support azure openai services for chat completion model #3668

[zwpaper]

otherwise LGTM