Validate feasibility of supporting new attribute types

[pellared]

What

Investigate whether it is possible and acceptable to extend the OTel Swift API and SDK with new attribute types.

Guidelines for evolving API/SDK: https://github.com/open-telemetry/opentelemetry-specification/blob/main/oteps/4485-extending-attributes-to-support-complex-values.md#how

Prototype in OTel Go demonstrating feasibility of adding new attribute types: open-telemetry/opentelemetry-go#6809

Why

Per open-telemetry/opentelemetry-specification#4602

Follows open-telemetry/opentelemetry-specification#4614

The goal is to make sure that PRs like these are acceptable for OTel Swift:

• all: drop attribute values restrictions opentelemetry-proto#707
• [EndGoal] [DoNotMerge] Extend the set of attribute value types opentelemetry-specification#4636

[bryce-b]

I believe we already support complex values to some extent, for example we allow heterogeneous arrays and sets via the AttributeArray and AttributeSet. Both of these are part of the AttributeValue

It appears the only thing we are missing is the null value

[bryce-b]

Should we create sub-issues and plan work to add the missing related features? (so far, it appears to be only NullValue)

[pellared]

@bryce-b, thanks for your response.

I believe we already support complex values to some extent, for example we allow heterogeneous arrays and sets via the AttributeArray and AttributeSet. Both of these are part of the AttributeValue

It appears the only thing we are missing is the null value

This issue was intended only to verify that you are good with the spec proposal. It looks like so. Therefore, I am closing the issue.

Should we create sub-issues and plan work to add the missing related features? (so far, it appears to be only NullValue)

Feel free to create the issues. Notice that the new attributes types are not stable yet in the specification. However, this also includes allow heterogeneous arrays and sets so maybe you want to add it sooner.