Allow specifying OpenAI-Organization header: (#313)

See https://platform.openai.com/docs/api-reference/introduction

> For users who belong to multiple organizations, you can pass a header
> to specify which organization is used for an API request. Usage from
> these API requests will count against the specified organization's
> subscription quota.

utils/server/index.ts

@@ -17,6 +17,9 @@ export const OpenAIStream = async (
     headers: {
       'Content-Type': 'application/json',
       Authorization: `Bearer ${key ? key : process.env.OPENAI_API_KEY}`,
+      ...(process.env.OPENAI_ORGANIZATION && {
+        'OpenAI-Organization': process.env.OPENAI_ORGANIZATION,
+      })
     },
     method: 'POST',
     body: JSON.stringify({