Search User Endpoint with lucene query not working well with some characters

Hi community,

we use the search user endpoint of the management-api to search for specific users. We build the query with the lucene syntax. We have some problems, when the query includes some special word-characters such as accents or umlauts.

The relevant part looks as follows:
given_name:(+T*) → the result includes all users whose given_names start with “T”. This works well and is what we expected.
given_name:(+Ü*) → there result always is empty, no user is found.

Depending on the character the same query seems to work differently. Is this a bug or something we have to treat differently?