docs: Add centralized credential management docs

docs/my-website/docs/proxy/configs.md

@@ -448,6 +448,33 @@ model_list:
 
 s/o to [@David Manouchehri](https://www.linkedin.com/in/davidmanouchehri/) for helping with this. 
 
+### Centralized Credential Management
+
+Define credentials once and reuse them across multiple models. This helps with:
+- Secret rotation
+- Reducing config duplication
+
+```yaml
+model_list:
+  - model_name: gpt-4o
+    litellm_params:
+      model: azure/gpt-4o
+      litellm_credential_name: default_azure_credential  # Reference credential below
+
+credential_list:
+  - credential_name: default_azure_credential
+    credential_values:
+      api_key: os.environ/AZURE_API_KEY  # Load from environment
+      api_base: os.environ/AZURE_API_BASE
+      api_version: "2023-05-15"
+    credential_info:
+      description: "Production credentials for EU region"
+```
+
+#### Key Parameters
+- `credential_name`: Unique identifier for the credential set
+- `credential_values`: Key-value pairs of credentials/secrets (supports `os.environ/` syntax)
+
 ### Load API Keys from Secret Managers (Azure Vault, etc)
 
 [**Using Secret Managers with LiteLLM Proxy**](../secret)
@@ -641,4 +668,4 @@ docker run --name litellm-proxy \
    ghcr.io/berriai/litellm-database:main-latest
 ```
 </TabItem>
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