implemented sending media type on token request (and others)

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

de.srsoftware.oidc.backend/src/main/java/de/srsoftware/oidc/backend/UserController.java

@@ -21,7 +21,6 @@ import jakarta.mail.*;
 import jakarta.mail.internet.*;
 import java.io.IOException;
 import java.time.Duration;
-import java.util.Comparator;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;