docs(openai): generate mintlify docs for openai

docs/docs.json

@@ -722,6 +722,7 @@
                 "group": "Openai",
                 "pages": [
                   "plugins/openai/overview",
+                  "plugins/openai/get-credentials",
                   "plugins/openai/api",
                   "plugins/openai/database"
                 ]

docs/plugins/openai/get-credentials.mdx

@@ -0,0 +1,32 @@
+---
+title: Get Credentials
+description: Step-by-step instructions for obtaining OpenAI API credentials.
+---
+
+## Authentication Method
+
+- **[`api_key`](/concepts/api-key)** - OpenAI API key
+
+## API Key Setup
+
+### Step 1: Get Your API Key
+
+1. Log in to [OpenAI Platform](https://platform.openai.com)
+2. Open **API keys** from the left sidebar
+3. Select **Create new secret key** and give it a name
+4. Copy the key and store it securely
+5. Add billing and credits as needed — API calls require paid usage
+
+**Storing Credentials:**
+
+```bash
+pnpm corsair setup --plugin=openai api_key=your-api-key
+```
+
+## Required Credentials Summary
+
+| Credential | Required For | Where to Find |
+|-----------|--------------|---------------|
+| API Key | All API calls | OpenAI Platform → API keys |
+
+For general information about how Corsair handles authentication, see [Authentication](/concepts/auth).