Fix typing of associations in user model

app/models/user.py

@@ -1,5 +1,5 @@
 "Script for everything User related in the database"
-from typing import List
+from typing import List, Optional
 
 from models import db
 
@@ -25,7 +25,7 @@ class User(db.Model):
     def association_list(self) -> List[str]:
         return self.associations.split(",")
 
-    def configure(self, username: str, admin: bool, bias: int, associations: List[str] = None) -> None:
+    def configure(self, username: str, admin: bool, bias: int, associations: Optional[List[str]] = None) -> None:
         """Configure the User"""
         if associations is None:
             associations = []