chore: integrate Prometheus

[kevcodez]

• Integrate Prometheus and expose via /metrics endpoint
• Add custom metrics to help identify operational issues
• Added missing log in case of server errors
• Increases webhook max size to 10 MB
• Bumped deps to resolve security warning
• Metrics for pg pool to potentially flag bottleneck

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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📝 Walkthrough

Summary by CodeRabbit

• New Features

  • Prometheus metrics for webhook processing, delays, DB pool stats and internal server errors; exposed at /metrics and toggleable via PROMETHEUS_METRICS_ENABLED

• Improvements

  • Webhook processing now records and exposes event-type and processing latency
  • Increased maximum webhook payload size
  • Error handling improved to avoid leaking internal details

• Tests

  • Added test coverage for the /metrics endpoint

• Chores

  • Updated dependency versions across the repo

Walkthrough

This PR integrates Prometheus into the Fastify app and adds business metrics for webhook processing. A new prometheus module defines counters, a histogram, and gauges; orb-sync-lib now returns { eventType, timeSinceEventCreatedMs }. Webhook handling records processed counts and delay, the Fastify app conditionally registers a /metrics endpoint (controlled by PROMETHEUS_METRICS_ENABLED) and wires prom-client to fastify-metrics. A custom error handler increments an internal-server-error metric for 5xx errors. Dependency version bumps and a test validating /metrics exposure were added.

Sequence Diagram(s)

sequenceDiagram
  participant Sender as Webhook Sender
  participant Fastify as Fastify App
  participant OrbSync as orb-sync-lib
  participant Prom as Prometheus (prom-client / /metrics)

  Sender->>Fastify: POST /webhooks (payload, headers)
  Fastify->>OrbSync: processWebhook(payload, headers)
  OrbSync-->>Fastify: { eventType, timeSinceEventCreatedMs }
  Fastify->>Prom: webhooksProcessedCounter.inc(eventType)
  Fastify->>Prom: webhookDelayMsHistogram.observe(eventType, timeSinceEventCreatedMs)
  Note right of Fastify: On 5xx errors -> internalServerErrorsCounter.inc()
  Prom->>Client: GET /metrics (scrape)

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Assessment against linked issues

Objective	Addressed	Explanation
Integrate Prometheus client into fastify-app [BILLING-2055]	✅
Expose /metrics endpoint [BILLING-2055]	✅
Include webhook delay metric [BILLING-2055]	✅
Expose additional business metrics [BILLING-2055]	✅

Out-of-scope changes

Code Change	Explanation
Tooling dependency version bumps (package.json)	Root-level tooling and TypeScript/eslint/turbo version bumps are unrelated to the Prometheus integration objective.
JSON formatting changes in webhook test fixture (apps/node-fastify/src/test/orb/subscription.json)	Whitespace/linebreak-only reformatting of test fixture does not affect the Prometheus integration requirements.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@apps/node-fastify/src/prometheus.ts`:
- Line 6: The CI fails because explicit "as any" casts are used when
constructing prom-client metrics; replace those casts with the correct
prom-client types: change the type of the config parameter/variable to the
appropriate prom-client config interface (e.g., client.CounterConfiguration) and
remove "as any" so you call new client.Counter(config) with a properly typed
config; do the same for the other occurrence (line 11) using the corresponding
prom-client metric config type (use client.<MetricName>Configuration or import
the specific type) and update any variable signatures so TypeScript infers the
correct types instead of using "any".