GetMetricMetadata returns no type for distribution metric

[rrey]

Describe the bug

The GetMetricMetadata endpoint returns an empty object for a Distribution that was just emitted.
For a Counter metric, the endpoint will return a minimal object with type specified. I expected to have the distribution type provided.

To Reproduce
Steps to reproduce the behavior:

Using the samples from the doc (edit the metric names)

1. Emit a distribution point: https://docs.datadoghq.com/api/latest/metrics/?code-lang=go#submit-distribution-points
2. Emit a Counter : (edited the metric type to datadogV2.METRICINTAKETYPE_COUNT.Ptr(): https://docs.datadoghq.com/api/latest/metrics/?code-lang=go#submit-metrics
3. Call metric metadata endpoint for the 2 metrics.
4. See the outputs:

For the counter:

Response from `MetricsApi.GetMetricMetadata`:
{
  "type": "count"
}

For the Distribution:

Response from `MetricsApi.GetMetricMetadata`:
{}

Expected behavior
For the distribution I would expect a distribution type:

Response from `MetricsApi.GetMetricMetadata`:
{
  "type": "distribution"
}

Additional context

N/A

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