[Evaluation] add environment variable for API token refresh rate (#38162)

* use env var for azure token refresh interval

* update changelog and set default value for env var

* cast refresh rate to int

* fix pylint error

* fix tox black issue

Author: slister1001

sdk/evaluation/azure-ai-evaluation/CHANGELOG.md

@@ -9,6 +9,7 @@
 
 ### Bugs Fixed
 - Output of adversarial simulators are of type `JsonLineList` and the helper function `to_eval_qr_json_lines` now outputs context from both user and assistant turns along with `category` if it exists in the conversation
+- Fixed an issue where during long-running simulations, API token expires causing "Forbidden" error. Instead, users can now set an environment variable `AZURE_TOKEN_REFRESH_INTERVAL` to refresh the token more frequently to prevent expiration and ensure continuous operation of the simulation. 
 
 ### Other Changes
 - Refined error messages for serviced-based evaluators and simulators.

sdk/evaluation/azure-ai-evaluation/azure/ai/evaluation/simulator/_model_tools/_identity_manager.py

@@ -14,7 +14,9 @@
 from azure.core.credentials import AccessToken, TokenCredential
 from azure.identity import DefaultAzureCredential, ManagedIdentityCredential
 
-AZURE_TOKEN_REFRESH_INTERVAL = 600  # seconds
+AZURE_TOKEN_REFRESH_INTERVAL = int(
+    os.getenv("AZURE_TOKEN_REFRESH_INTERVAL", "600")
+)  # token refresh interval in seconds
 
 
 class TokenScope(Enum):