Allows OpenAI-Key to be set in header for /converse and /chat endpoints.

[rithviknishad]

• Fixes Allow API key overrides to /chat and /converse endpoints #39

Changes:

• Adds field to User model: allow_key
• Uses OpenAI-Key from the headers if present. Else falls back to using the OpenAI API key from settings if allow_key for user is True.
• Raises ValidationError if either was not provided. Validation performed at perform_create and converse actions.

[ishanExtreme]

@skks1212 @rithviknishad
if we are allowing user giving the api request to set "allow" variable on their own in the request body, then our api will not safe to be made public. Instead if we can create a new field in user model specifying if "special/nurse" or not and use our api key in that case. So normal user have to send the api_key everytime 🤔

[shivankacker]

@ishanExtreme yep that is how it is planned to be. @rithviknishad I have suggested changes 😬

[shivankacker]

LGTM