Added support for passing the openai_organization as an argument, as it
was only supported by the environment variable but openai_api_key was
supported by both environment variables and arguments.
`ChatOpenAI(temperature=0, model_name="gpt-4", openai_api_key="sk-****",
openai_organization="org-****")`
Add support for defining the organization of OpenAI, similarly to what
is done in the reference code below:
```
import os
import openai
openai.organization = os.getenv("OPENAI_ORGANIZATION")
openai.api_key = os.getenv("OPENAI_API_KEY")
```
vinoyang