refactor mongo entities, optimize imports

examples/basic-auth/src/main/java/org/keycloak/example/basicauth/BasicAuthService.java

@@ -21,10 +21,7 @@ import org.jboss.resteasy.annotations.cache.NoCache;
 
 import javax.ws.rs.GET;
 import javax.ws.rs.Path;
-import javax.ws.rs.Produces;
 import javax.ws.rs.QueryParam;
-import java.util.ArrayList;
-import java.util.List;
 
 /**
  * @author <a href="mailto:bill@burkecentral.com">Bill Burke</a>