Add Grafana dashboards for PostGuard usage stats on Scaleway

[rubenhensen]

Summary

Set up Grafana dashboards on our Scaleway hosting to track PostGuard usage statistics across all channels.

Metrics to track

Messages sent (broken down by channel)

• Via postguard.eu (production website)
• Via staging.postguard.eu
• Via Outlook extension
• Via Thunderbird extension
• Via API keys (programmatic usage)

Storage

• Cryptify storage usage on staging
• Cryptify storage usage on Procolix production environment

Details

• Cryptify needs to expose metrics (e.g., Prometheus endpoint or structured logs) for:
  • Upload count and size per channel/source
  • Current total storage used
  • File count (active / expired)
• The channel/source can be derived from request headers, API key presence, or a client identifier.
• Grafana dashboards should be set up on the existing Scaleway Grafana instance.

Related issues

• Enforce server-side upload limits: 5 GB rolling per email (14 days) #100 (server-side limits — usage tracking is a prerequisite)

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/dobby please pick this up. Pull new commits and make new commits to the dobby repo often to tell other dobbies what you are up to, since several issues are interconnected. Tag @rubenhensen for anything you can't solve.

[dobby-coder]

🧦 Dobby is on it, sir/madam! Dobby has heard the call and is eager to help! Dobby will pull the latest commits from his memory repository, check what the other dobbies have been up to, and make notes often so nobody steps on each other's toes. Dobby will tag @rubenhensen if Dobby gets stuck!

[rubenhensen]

/dobby please pick this up. First check the other related issues and their comments/PRs — another dobby may have already done some of this work. Pull new commits and make new commits to the dobby repo often to tell other dobbies what you are up to, since several issues are interconnected. Tag @rubenhensen for anything you can't solve.

[dobby-coder]

Dobby is back, sir! Dobby will first check the memory repo and the other related cryptify issues (like #100) to see what previous dobbies have already done. Then Dobby will pick up the Grafana dashboards work from wherever it was left off. Dobby will commit to the memory repo often!

[dobby-coder]

Dobby has opened draft PR #102 with the server-side half of this issue: a Prometheus /metrics endpoint with per-channel upload counters and storage gauges, plus a ready-to-import Grafana dashboard JSON under docs/grafana/.

Dobby kept the metrics PR strictly separate from #100's sender-email tracking so the two can land independently. The addons (Outlook + Thunderbird) still need a small follow-up each to set X-Cryptify-Source — Dobby called those out in the PR body as follow-ups.

Draft pending: (1) confirmation that the Scaleway / Procolix network policy restricts /metrics to the Prometheus segment, and (2) a staging scrape test. Tagging @rubenhensen for the network policy question.