Discrepancy between metrics names in prometheus and metadata

Hello,

When creating a Counter metric with client_python 0.4.0 - 0.16.0:

my_metric_count = Counter(name='my_metric_count',
                      documentation='My helpful description',
                      registry=MY_REGISTRY)

The metric will show in prometheus as my_metric_count_total. This is absolutely fine with the world however that same metric will show under http://prometheus:9090/api/v1/metadata as the original name:

    "my_metric_count": [
      {
        "type": "counter",
        "help": "My helpful description",
        "unit": ""
      }
    ],

If one creates the metric with '_total' suffix:

my_metric_count = Counter(name='my_metric_count_total',
                      documentation='My helpful description',
                      registry=MY_REGISTRY)

It will show in prometheus as that exact name my_metric_count_total but the name in the /api/v1/metadata will now be truncated.

    "my_metric_count": [
      {
        "type": "counter",
        "help": "My helpful description",
        "unit": ""
      }
    ],

This breaks certain input plugins with telegraf that rely on the prometheus metadata and remote write to fetch the metric type. Version of this library starting with 0.4.0 exhibit this behavior which is when metrics names began to be munged with '_total' for compatibility with OpenMetrics.

Thank you.

Inizia tracciando come vengono normalizzati i nomi dei Counter e come i metadati vengono esposti tramite /api/v1/metadata, usando i due esempi nell’issue come riproduzioni. Confronta il nome di esposizione di Prometheus con la chiave dei metadati e aggiungi una copertura di regressione che mostri una denominazione coerente per i Counter creati con e senza il suffisso _total.