docs: protected String getAlternatePrincipal(final X509Certificate certificate) {
          if (alternatePrincipalAttribute == null) {
              return null;
          }
          val attributes = extractPersonAttributes(certificate);
          val attribute = attributes.get(alternatePrincipalAttribute);
          if (attribute == null) {
              LOGGER.debug("Attempt to get alternate principal with attribute [{}] was unsuccessful.", alternatePrincipalAttribute);
              return null;
          }
          val optionalAttribute = CollectionUtils.firstElement(attribute);
          if (optionalAttribute.isEmpty()) {
              LOGGER.debug("Alternate attribute list for [{}] was empty.", alternatePrincipalAttribute);
              return null;
          }
          val alternatePrincipal = optionalAttribute.get().toString();
          if (StringUtils.isNotEmpty(alternatePrincipal)) {
              LOGGER.debug("Using alternate principal attribute [{}]", alternatePrincipal);
              return alternatePrincipal;
          }
          LOGGER.debug("Returning null principal id...");
          return null;
      }