Add optional model configuration

[JairoGuo]

🔖 Enhancement description

Add a large model compatible with OpenAI protocol to the assistant

🎤 Pitch

.env:

_APP_ASSISTANT_OPENAI_API_KEY=YOUR_OPENAI_API_KEY _APP_ASSISTANT_BASE_URL=https://api.openai.com/v1 _APP_ASSISTANT_MODEL_NAME=gpt-4o _APP_ASSISTANT_EMBEDDING_MODEL=text-embedding-ada-002

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