Database connection pool semantic conventions

[mateuszrzeszutek]

What are you trying to achieve?

Before OTel metrics API went stable, in Splunk Java distro we have implemented several instrumentations that collect metrics from various JDBC connection pool libraries (using micrometer). Now that metrics API is stable, we want to upstream these - and for this to happen we need to have semantic conventions describing DB connection pool metrics.

Here's what we currently have in the Splunk distro: https://github.com/signalfx/splunk-otel-java/blob/main/docs/metrics.md#connection-pool-metrics
We've instrumented most (if not all) JDBC connection pool libraries available for Java users; the instruments described in the link above are what we came up with that fits all of those libs.

I'm planning to create a PR that ports these conventions over to the OTel spec; is there anything that I should take into consideration beforehand? E.g. any other utilities from other languages? (this is probably more of a question to the general community)

Additional context.

Splunk DB connection pool metrics: https://github.com/signalfx/splunk-otel-java/blob/main/docs/metrics.md#connection-pool-metrics