OpenTelemetry Specification parity

[ChrisLightfootWild]

Is your feature request related to a problem?
At the time of writing, the most recent tagged release of the specification is 1.32.0.

There are several references throughout the API/SDK to the specification, but it looks like the most recent is ~1.21.

Describe the solution you'd like
A better understanding of what features may be lagging behind.

I had a use-case to add a SpanLink to an existing span which is now permitted and stable as per 1.31.0, with initial experimental availability from 1.27.0.

Describe alternatives you've considered
Do we have to be fully compliant with each version of the spec before implementing the newer parts? (Probably! 🤔)

Additional context
Discussed in the SIG today, with a view to opening an issue for visibility.

• Add Span::addLink() and Meter::createGauge() #1289
• implement events v1.32 #1291
• update ReadWriteLogRecord Fix what can be modified via ReadWriteLogRecord opentelemetry-specification#3907
• SDK configuration from https://github.com/open-telemetry/opentelemetry-specification/releases/tag/v1.32.0

[brettmc]

Partly resolved by #1289

[Nevay]

Metrics SDK changes:

• MetricProducer (v1.16.0, stable since v1.25.0), can replace MetricSourceRegistryInterface and logic in ExportingReader::add()

  The SDK’s in-memory state MAY implement the MetricProducer interface for convenience.

• MetricFilter¹ (v1.29.0, experimental), used by MetricProducer
• Cardinality limits¹ (v1.21.0, experimental)

Footnotes

1. If someone wants to pick one of these up; implementation diverged a bit since the initial port, but should at least give a rough outline:
   MetricFilter: https://github.com/Nevay/otel-sdk-metrics/commit/4a52d65f009e3e28771a9a0cf828a6acf2d43f5a
   Cardinality limits: https://github.com/Nevay/otel-sdk-metrics/commit/9a98e451bad4155b31be844a95f7057e38534b83 ↩ ↩²