Provide option to use actual OpenAI Backends.

[prasann]

Currently, USE_SIMULATOR flag will control the deployment of the simulator. However, when we set the value to false it breaks the deployment due to simulator_key.

There are few options,

• 1. Along with URLs as env, get their corresponding keys as well from .env
• 2. Make simulator_key as optional, provide guidance to use api_key as a header

This issue is for a: (mark with an x)

- [ ] bug report -> please search issues before submitting
- [x ] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)