code: @SneakyThrows
      public static PrivateKey extractPrivateKeyFromResource(final String signingSecretKey) {
          LOGGER.debug("Attempting to extract private key...");
          val resource = ResourceUtils.getResourceFrom(signingSecretKey);
          val factory = new PrivateKeyFactoryBean();
          factory.setAlgorithm(RsaKeyUtil.RSA);
          factory.setLocation(resource);
          factory.setSingleton(false);
          return factory.getObject();
      }
docs: Extract private key from resource private key.
  
  @param signingSecretKey the signing secret key
  @return the private key