[FR] Use dotenv to populate user settings and credentials

[erdincka]

Is your feature request related to a problem? Please describe.
Instead of user editing .venv/bin/activate script we can use Python dotenv library to automatically load API key and other variables specific to the user.

Describe the solution you'd like
Simply adding this code in ./self_serve_platform/system/config.py, we would be automatically load required/customised variables to the app's running environment.

from os.path import join, dirname
from dotenv import load_dotenv

dotenv_path = join(dirname(__file__), '.env')
load_dotenv(dotenv_path)

This would require change to the documentation to inform user that they should create an .env file with the content for their API keys and endpoints etc.

Describe alternatives you've considered

Current method works fine.

[noorul]

Not sure why we are not using pydantic-settings