[BUG] usernames can contain uppercase characters but this breaks own_index type patterns

[sebovzeoueb]

I've been trying to implement a system similar to the own_index using the username in an index pattern, however my usernames come from the OpenID sub claim which can (and does) contain uppercase characters, as can OpenSearch Security usernames in general. Thus the index pattern the user has access to contains uppercase characters.

There's one small issue with this: OpenSearch doesn't allow uppercase characters in index names. It's therefore impossible to create an index that matches the pattern the user can access!