Revise handling of query param with no value in URLUtils.parseParameters

[Yavor Vasilev]

    public void testParseParameters_paramWithNoValue() {

        String query = "response_type=code" +
                "&client_id=s6BhdRkqt3" +
                "&redirect_uri=" +
                "&scope=read";

        Map<String,List<String>> params = URLUtils.parseParameters(query);

        assertEquals(Collections.singletonList("code"), params.get("response_type"));
        assertEquals(Collections.singletonList("s6BhdRkqt3"), params.get("client_id"));
        assertEquals(Collections.singletonList(""), params.get("redirect_uri"));
        assertEquals(Collections.singletonList("read"), params.get("scope"));
    }

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