custom overflowSet in metrics aggregate

[timannguyen]

Problem Statement

A clear and concise description of what the problem is.
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when I set cardinality limit with OTEL_GO_X_CARDINALITY_LIMIT, there is no means to set the default attr for the overflow set.

https://github.com/open-telemetry/opentelemetry-go/blob/main/sdk/metric/internal/aggregate/limit.go#L11

Proposed Solution

To implement a set function to update the overflowSet

Alternatives

No alternative when cardinality is limited

Prior Art

N/A

Additional Context

When data is ingested into splunk, the search would ignore metrics that do not have those attributes when queried. By setting attributes as empty string or default value instead of not having them, Splunk will include the overflow set as part of the query when aggregating or searching metrics.