Create update_username functions for category and table.

classes/category.py

@@ -188,3 +188,27 @@ class Category:
             str: string of json representation of Category
         """
         return json.dumps(self.to_dict(), indent=4)
+
+    def update_username(self, old_username: str, new_username: str) -> bool:
+        """
+        Checks score map for old username. Pops old username to remove from map.
+        Updates score's username and calls self.add_score with new score to add back
+        to map and sort.
+
+        Args:
+            old_username (str): Username to replace
+            new_username (str): Username to replace with
+
+        Returns:
+            bool: True indicating a score was updated, False otherwise
+        """
+
+        ret_val: bool = False
+
+        if old_username in self._scores_map:
+            ret_val = True
+            score: Score = self._scores_map.pop(old_username)
+            score.user = new_username
+            self.add_score(score)
+
+        return ret_val