Add slash restriction to username validation

nativeauthenticator/handlers.py

@@ -100,15 +100,15 @@ def get_result_message(
             if minimum_password_length > 0:
                 message = (
                     "Something went wrong!\nBe sure your username "
-                    "does not contain spaces or commas, your "
+                    "does not contain spaces, commas or slashes, your "
                     f"password has at least {minimum_password_length} "
                     "characters and is not too common."
                 )
             # Error if minimum password length is 0.
             else:
                 message = (
                     "Something went wrong!\nBe sure your username "
-                    "does not contain spaces or commas and your "
+                    "does not contain spaces, commas or slashes and your "
                     "password is not too common."
                 )
         # If user creation went through & open-signup is enabled, success.

nativeauthenticator/nativeauthenticator.py

@@ -391,7 +391,7 @@ def change_password(self, username, new_password):
         return True
 
     def validate_username(self, username):
-        invalid_chars = [",", " "]
+        invalid_chars = [",", " ", "/"]
         if any((char in username) for char in invalid_chars):
             return False
         return super().validate_username(username)