Check Umlauts and other non-ASCII characters in advanced queries

[fengelniederhammer]

Check how they are handled. We should support non-ASCII in advanced queries.

From https://cevo-group.slack.com/archives/C01M74N29RD/p1773652139586119

I tried an Umlaut in advanced queries:

It works when quoted: https://lapis.cov-spectrum.org/open/v2/sample/aggregated?advancedQuery=division.regex%3D%27Graub%C3%BCnden%27&
It doesn't work when not quoted: https://lapis.cov-spectrum.org/open/v2/sample/aggregated?advancedQuery=division.regex%3DGraub%C3%BCnden&