Mark ExplicitBucketBoundaries hint API as stable

[trask]

What are you trying to achieve?

Mark ExplicitBucketBoundaries hint API as stable since this will be required for emitting HTTP semantic conventions now that we are changing http.server.duration and http.client.duration unit from milliseconds to seconds (see #3390).

[MrAlias]

It seems like we should have a few implementations of this API before we stabilize it, right?

[trask]

ya, the HTTP semconv stability WG would be very grateful if any other languages besides Java can implement since it is required for HTTP semconv stability

[trask]

@reyang will be prototyping in .NET ❤️

we will need to prototype in one more language

cc @open-telemetry/python-approvers @open-telemetry/cpp-approvers @open-telemetry/javascript-approvers @open-telemetry/go-approvers 🤞

[MrAlias]

Go might be able to prototype this in a few weeks if we stabilize the metric API first.

[trask]

related #3621

[trask]

related #3622

[legendecas]

JS implementation: open-telemetry/opentelemetry-js#3876

[dyladan]

JS prototype looks fine to me

[trask]

@open-telemetry/dotnet-maintainers have you had a chance to prototype this in .NET? I think we just need one more (we now have Java and JS prototypes).

[MrAlias]

I think we need resolutions to the following issues before we can proceed with this:

• Consider allowing a simpler API for histogram default buckets #3621
• Consider making Advice non-identifying for instruments #3622

[trask]

Just checking in on this, I think we only have 2 of the 3 required prototypes needed to mark this stable:

• Prototype histogram advice API (i.e. Hints) opentelemetry-java#5217
• feat(metrics): prototype experimental advice support opentelemetry-js#3876

[MrAlias]

@trask: Go prototype open-telemetry/opentelemetry-go#4341

Thanks @dashpole 🎉

[albertored]

A little late but also Erlang/Elixir implementation is in PR open-telemetry/opentelemetry-erlang#628