feat(metering-and-billing): drift-check for plugin event dimensions

[gergely-kurucz-konghq]

Description

Adds tooling + a scheduled workflow that keep the docs' "Captured event dimensions" reference (on the Metering & Billing plugin page) in sync with the fields the plugin actually emits.

What

• tools/mb-event-dimensions/ (Node, ESM):
  • extract-catalog.js — reads the LuaLS --doc export (doc.json) of kong-ee cloudevent.lua and emits the emitted-event field catalog (per event type, inheritance resolved).
  • check-drift.js — compares that catalog against a committed snapshot (event-fields.snapshot.json) and the rendered data file (app/_data/plugins/metering-and-billing.yaml); prints added / removed / type-changed fields and exits non-zero on drift.
  • README.md with usage + example output.
• .github/workflows/watch-mb-cloudevent.yml — daily (schedule + workflow_dispatch + optional repository_dispatch); checks out kong-ee, runs the check, and on drift bumps the snapshot, opens a PR, and pings docs maintainers via Slack.

Why

The event-dimension reference is hand-authored from cloudevent.lua and would silently drift as the plugin evolves. This turns drift into a dated alert PR instead of a stale doc.

How

The plugin's emitted fields are declared as LuaLS ---@class/---@field annotations in kong-ee (separate PR); lua-language-server --doc exports them to doc.json, which these scripts consume — a declared, stable source rather than scraping imperative code. Verified end-to-end against the annotated cloudevent.lua (clean = exit 0; add/remove/type-change = exit 1 with a clear diff).

Fixes https://konghq.atlassian.net/browse/OM-433

Dependencies / sequencing

• Base branch: feat(docs): document Metering & Billing plugin event dimensions #6538 (needs the metering-and-billing.yaml data file added there).
• Requires the kong-ee cloudevent.lua LuaLS-annotations PR to land (source of doc.json).
• Adds one new CI dependency: a pinned lua-language-server release (installed in the workflow).

Checklist

• Tooling verified locally (extract + drift-check against the real annotated file).
• Tested how-to docs. — N/A (no page content changed; tooling + CI only).
• No new docs pages (no index updates needed).
• Merge after its base branch and the kong-ee annotations PR.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}