public Claims getPayload(final String jwt) {
        return Jwts.parser()
                .verifyWith(tokenConfigurationParameter.getPublicKey())
                .build()
                .parseSignedClaims(jwt)
                .getPayload();
    }
@Test
    void givenJwt_whenGetPayload_thenReturnPayload() {
        // Given
        String token = Jwts.builder()
                .claim("user_id", "12345")
                .issuedAt(new Date())
                .expiration(new Date(System.currentTimeMillis() + 86400000L)) // 1 day expiration
                .signWith(keyPair.getPrivate())
                .compact();

        // When
        Claims payload = tokenService.getPayload(token);

        // Then
        assertThat(payload.get("user_id")).isEqualTo("12345");

    }