public Map<String, Set<String>> getAvailableTags(Collection<Meter> meters) {
        Map<String, Set<String>> availableTags = new HashMap<>();
        for (Meter meter : meters) {
            for (Tag tag : meter.getId()
                    .getTagsAsIterable()) {
                Set<String> value = Collections.singleton(tag.getValue());
                // tag.getKey() e.g. "total", "max", "count", "value" etc.
                availableTags.merge(tag.getKey(), value, Sets::union);
            }
        }
        return availableTags;
    }
@author James Chen
@implNote We don't cache because the metrics in the registry may change especially the metrics of
          turms service requests
turms-server-common/src/main/java/im/turms/server/common/infra/metrics/MetricsPool.java