WIP checkpoint: Enforce 18+ age gate at account registration

backend/app/routers/auth.py

@@ -1,6 +1,6 @@
 """Authentication router - login, register, token refresh."""
 
-from datetime import datetime, timedelta, timezone
+from datetime import date, datetime, timedelta, timezone
 
 from fastapi import APIRouter, Depends, HTTPException, status
 from fastapi.security import OAuth2PasswordRequestForm
@@ -77,9 +77,19 @@ def hash_password(password: str) -> str:
     return pwd_context.hash(password)
 
 
-def calculate_age(birth_date: datetime) -> int:
-    """Calculate age in years from a birth date."""
-    today = datetime.now(timezone.utc).date()
+def calculate_age(birth_date: date, today: date | None = None) -> int:
+    """Calculate age in years from a birth date.
+
+    Args:
+        birth_date: The person's date of birth.
+        today: The reference date. Defaults to today's date (UTC).
+
+    Returns:
+        Age in whole years as of the reference date.
+    """
+    if today is None:
+        today = datetime.now(timezone.utc).date()
+
     age = today.year - birth_date.year
     # Adjust if birthday hasn't occurred yet this year
     if (today.month, today.day) < (birth_date.month, birth_date.day):