feat: add utility function to retrieve user by username or email

Author: BryanttV

openedx_authz/rest_api/utils.py

@@ -0,0 +1,26 @@
+"""Utility functions for the Open edX AuthZ REST API."""
+
+from django.contrib.auth import get_user_model
+from django.db.models import Q
+
+User = get_user_model()
+
+
+def get_user_by_username_or_email(username_or_email: str) -> User:
+    """
+    Retrieve a user by their username or email address.
+
+    Args:
+        username_or_email (str): The username or email address to search for.
+
+    Returns:
+        User: The User object if found and not retired.
+
+    Raises:
+        User.DoesNotExist: If no user matches the provided username or email,
+            or if the user has an associated retirement request.
+    """
+    user = User.objects.get(Q(email=username_or_email) | Q(username=username_or_email))
+    if hasattr(user, "userretirementrequest"):
+        raise User.DoesNotExist
+    return user