[Feat-Proxy] Slack Alerting - allow using os.environ/ vars for alert to webhook url (#5726)

* allow using os.environ for slack urls

* use env vars for webhook urls

* fix types for get_secret

* fix linting

* fix linting

* fix linting

* linting fixes

* linting fix

* docs alerting slack

* fix get data

litellm/integrations/SlackAlerting/utils.py

@@ -0,0 +1,51 @@
+"""
+Utils used for slack alerting
+"""
+
+from typing import Dict, List, Optional, Union
+
+import litellm
+from litellm.proxy._types import AlertType
+from litellm.secret_managers.main import get_secret
+
+
+def process_slack_alerting_variables(
+    alert_to_webhook_url: Optional[Dict[AlertType, Union[List[str], str]]]
+) -> Optional[Dict[AlertType, Union[List[str], str]]]:
+    """
+    process alert_to_webhook_url
+    - check if any urls are set as os.environ/SLACK_WEBHOOK_URL_1 read env var and set the correct value
+    """
+    if alert_to_webhook_url is None:
+        return None
+
+    for alert_type, webhook_urls in alert_to_webhook_url.items():
+        if isinstance(webhook_urls, list):
+            _webhook_values: List[str] = []
+            for webhook_url in webhook_urls:
+                if "os.environ/" in webhook_url:
+                    _env_value = get_secret(secret_name=webhook_url)
+                    if not isinstance(_env_value, str):
+                        raise ValueError(
+                            f"Invalid webhook url value for: {webhook_url}. Got type={type(_env_value)}"
+                        )
+                    _webhook_values.append(_env_value)
+                else:
+                    _webhook_values.append(webhook_url)
+
+            alert_to_webhook_url[alert_type] = _webhook_values
+        else:
+            _webhook_value_str: str = webhook_urls
+            if "os.environ/" in webhook_urls:
+                _env_value = get_secret(secret_name=webhook_urls)
+                if not isinstance(_env_value, str):
+                    raise ValueError(
+                        f"Invalid webhook url value for: {webhook_urls}. Got type={type(_env_value)}"
+                    )
+                _webhook_value_str = _env_value
+            else:
+                _webhook_value_str = webhook_urls
+
+            alert_to_webhook_url[alert_type] = _webhook_value_str
+
+    return alert_to_webhook_url