Allow API key overrides to /chat and /converse endpoints

[skks1212]

As Ayushma will be open to all, it is not viable to have everyone be able to use our Open AI api keys. We should only allow a set number of users to use Ayushma's OpenAI key.

So, add a boolean field called allow_key (or any other name that you think would be more fit) with default false to the user model. Allow /chat and /converse endpoints to have an open_ai_key parameter to be sent in the request headers. Now check if open_ai_key is present in the request headers.

• If it is, use that key.
• If the key is not present in the request headers, and the allow_key value is True on the requesting user, use the default OPEN_AI_KEY.
• If the key is not present in the headers, and the allow_key is False, respond with an error message asking for an open_ai_key