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

👀 Have you spent some time to check if this issue has been raised before?

• I checked and didn't find similar issue

🏢 Have you read the Code of Conduct?

• I have read the Code of Conduct