Grafana datasource plugin for B2C Commerce (Metrics + CIP) with Go SDK

[clavery]

Summary

Adds a Grafana datasource plugin for B2C Commerce with two datasource types, plus a standalone Go SDK that powers them (and is reusable for other Go tooling). Verified end-to-end against a live instance.

New packages

• packages/b2c-tooling-sdk-go — standalone Go SDK (git-tag versioned): OAuth client-credentials auth, a Metrics REST client (with transparent >24h range partitioning + typed HTTPError), a CIP Avatica/protobuf client, tenant/window helpers, and tag enrichment kept byte-parity with the TS SDK via a golden fixture.
• packages/b2c-grafana-datasource — the plugin (git-tag versioned), shipping two datasource types from one workspace package:
  • Metrics (SCAPI Observability): tiered push-down/label filters, metric multi-select, group-by legends, live discovery + template variables.
  • CIP (Commerce Intelligence): raw Calcite SQL built on grafana/sqlds/v4 (the framework the built-in Postgres/MySQL datasources use) — $__timeFilter/$__timeGroup/$__interval macros, schema browser, template variables.
  • React query editors, a multi-stage Docker demo (synthetic mock and live-instance mode), and merchant + technical dashboards.

Also

• @salesforce/b2c-tooling-sdk: metrics tag enrichment refactored into a declarative catalog + golden fixture (the shared source of truth the Go SDK consumes). No API change (see changeset).
• Error-source attribution (429 → downstream, not a plugin fault), authoritative RefID keying, sqlds row limits/timeouts, idempotent timestamp normalization.
• CI: a test-go job builds/vets/tests both Go modules; a catalog-parity test guards TS↔Go drift.

Versioning

The Grafana plugin and Go SDK are git-tag versioned (like b2c-vs-extension), not changesets. The changeset in this PR covers only the @salesforce/b2c-tooling-sdk enrichment change.

Manual testing

Requires Docker and the b2c CLI configured for a B2C instance with the Metrics closed beta enabled and CIP access.

cd packages/b2c-grafana-datasource
make demo                    # synthetic data, no credentials — open http://localhost:3000
make real INSTANCE=<name>    # live instance (creds sourced from the b2c CLI keychain)

In Grafana (http://localhost:3000, anonymous admin):

• Open the provisioned dashboards (Metrics demo, CIP merchant, CIP technical) and confirm panels render.
• Metrics editor: pick a category + metric(s), add server/label filters, group-by; confirm a "Last 7 days" range works (partitioned).
• CIP editor: run a $__timeGroupAlias(col, $__interval) + $__timeFilter(col) query in both Time series and Table format; use the schema browser and a $site template variable.
• make down to tear down.

Draft — opening for review of the overall architecture and to run CI. Rate-limit resilience (retry/caching) is planned separately in packages/b2c-grafana-datasource/RESILIENCE_PLAN.md.