Add Metrics sections to RPC system-specific conventions

[Copilot]

Plan: Add Metrics Sections to RPC System-Specific Conventions

• Add Metrics section to JSON-RPC documentation (docs/rpc/json-rpc.md)
  • Add "Metrics" to table of contents
  • Add metrics section at the end with reference to general RPC Metrics
  • Specify rpc.system.name MUST be set to "jsonrpc"
  • Use absolute path for rpc-metrics.md link
  • Restructure TOC with hierarchical Spans section
• Add Metrics section to gRPC documentation (docs/rpc/grpc.md)
  • Add "Metrics" to table of contents
  • Add metrics section at the end with reference to general RPC Metrics
  • Specify rpc.system.name MUST be set to "grpc"
  • Use absolute path for rpc-metrics.md link
  • Restructure TOC with hierarchical Spans section
• Add Metrics section to Connect RPC documentation (docs/rpc/connect-rpc.md)
  • Add "Metrics" to table of contents
  • Add metrics section at the end with reference to general RPC Metrics
  • Specify rpc.system.name MUST be set to "connectrpc"
  • Use absolute path for rpc-metrics.md link
  • Restructure TOC with hierarchical Spans section
• Validate the changes build correctly
• Request code review
• Address review feedback: Use absolute paths instead of relative paths
• Address review feedback: Restructure with hierarchical TOC
• Add changelog entry
• Properly rebase onto latest main (e126ea9)
• Fix Connect RPC system name value to "connectrpc"

Summary

Successfully added Metrics sections to all three RPC system-specific convention documents (JSON-RPC, gRPC, and Connect RPC), following the established pattern from database-specific conventions. Updated all links to use absolute paths for better robustness. Restructured the table of contents and content to have a hierarchical organization:

• Spans
  • Client
  • Server
• Metrics

Added changelog entry documenting the enhancement with issue numbers [3319, 3320]. Properly rebased onto latest main (e126ea9) with 9 commits cleanly stacked on top. Connect RPC system name corrected to "connectrpc".

All validation checks passed:

• ✅ Markdown table of contents generated correctly with hierarchical structure
• ✅ Markdown linting passed
• ✅ Table check passed
• ✅ Schema check passed
• ✅ Code review completed with no issues
• ✅ Absolute paths applied to all rpc-metrics.md links
• ✅ Hierarchical TOC structure implemented
• ✅ Changelog entry added and validated with correct issue numbers
• ✅ Properly rebased onto latest main (e126ea9)
• ✅ Connect RPC system name corrected to "connectrpc"

Original prompt

---

This section details on the original issue you should resolve

<issue_title>RPC: mention metrics on system-specific conventions</issue_title>
<issue_description>We include metrics section in DB-specific conventions, e.g. https://github.com/open-telemetry/semantic-conventions/blob/main/docs/db/mysql.md#metrics

This allows us to specify system name on metrics and also document if there are any details when implementing metrics for this system. E.g. JSON-RPC metrics might include jsonrpc.protocol.version attribute and after #3317 we'd probably add url.scheme for grpc.

So we should

• add metrics section to JSON-RPC, gRPC and Connect-RPC docs
• it should be similar to "{Protocol} instrumentations SHOULD collect metrics according to the general Semantic Conventions for RPC Metrics.\n rpc.system.name MUST be set to {"protocol"}.
• update table of content in each doc</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes RPC: mention metrics on system-specific conventions #3319

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Copilot / name: copilot-swe-agent[bot] (07a02e4)
• ✅ login: lmolkova / name: Liudmila Molkova (61a734f)