Add RPC migration doc

[trask]

Resolves #3204

Marking as ready to start reviewing but will wait to merge until after #3223 is merged and that change incorporated.

[Copilot]

Pull request overview

This PR adds a comprehensive migration guide to help users transition from experimental RPC semantic conventions (v1.37.0) to the upcoming stable version. The document follows established patterns from HTTP and database migration guides, providing a structured approach for instrumentation maintainers to implement backward-compatible upgrades.

Key Changes:

• Added detailed RPC migration documentation covering span attributes, metrics, and their respective changes
• Documented the OTEL_SEMCONV_STABILITY_OPT_IN environment variable pattern for phased rollout
• Included comprehensive change tables for attribute renames, new attributes, and deprecated metrics
• Added changelog entry for the enhancement

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 7 comments.

File	Description
docs/non-normative/rpc-migration.md	New migration guide documenting changes to RPC semantic conventions including attribute renames (e.g., rpc.system → rpc.system.name), metric name changes (e.g., rpc.server.duration → rpc.server.call.duration), unit changes (ms → s), and deprecated metrics
.chloggen/rpc-migration-doc.yaml	Changelog entry for the RPC migration guide enhancement

[github-actions]

This PR has been labeled as stale due to lack of activity. It will be automatically closed if there is no further activity over the next 7 days.

[zeitlinger]

Implementation issue for Java: open-telemetry/opentelemetry-java-instrumentation#15871

[zeitlinger]

what is the expected behavior of span attributes with rpc/dup

• rpc.method: com.example.ExampleService/exampleMethod or exampleMethod?
• add network.type? (removed)
• add error.type? (added)

For DB stabilization, we added all, but there is no conflict:

https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/a8b98646fa53116db6d22d5b26b293bd0b1ad5af/instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/semconv/db/DbClientAttributesExtractor.java#L97-L117

[zeitlinger]

network.protocol.name is not conditional on being different from http - is this intentionally being different from https://github.com/thompson-tomo/semantic-conventions/blob/main/docs/http/http-spans.md#http-client-span ?

[trask]

what is the expected behavior of span attributes with rpc/dup

rpc/dup should give priority to stable semconv over old semconv where there are conflicts

[kamphaus]

Should docs/rpc/README.md be updated to include a link to docs/non-normative/rpc-migration.md similar to the HTTP readme?

For help migrating from non-stable to stable conventions, see [the migration guide](../non-normative/rpc-migration.md).