doc update and minor fix

docs/docs/usage-guide/changing_a_model.md

@@ -37,6 +37,17 @@ model="" # the OpenAI model you've deployed on Azure (e.g. gpt-4o)
 fallback_models=["..."]
 ```
 
+To use Azure AD (Entra id) based authentication set in your `.secrets.toml` (working from CLI), or in the GitHub `Settings > Secrets and variables` (working from GitHub App or GitHub Action):
+
+```toml
+[azure_ad]
+client_id = ""  # Your Azure AD application client ID
+client_secret = ""  # Your Azure AD application client secret
+tenant_id = ""  # Your Azure AD tenant ID
+api_base = ""  # Your Azure OpenAI service base URL (e.g., https://openai.xyz.com/)
+```
+
+
 Passing custom headers to the underlying LLM Model API can be done by setting extra_headers parameter to litellm.
 
 ```toml

pr_agent/algo/ai_handlers/litellm_ai_handler.py

@@ -100,6 +100,7 @@ class LiteLLMAIHandler(BaseAiHandler):
 
         # Check for Azure AD configuration
         if get_settings().get("AZURE_AD.CLIENT_ID", None):
+            from azure.identity import ClientSecretCredential
             self.azure = True
             # Generate access token using Azure AD credentials from settings
             access_token = self._get_azure_ad_token()