Add UTM parameters to links pointing at ohdear.app

[freekmurze]

Links to ohdear.app now carry UTM parameters so we can tell which channel drove the click. Tracked domains live in config/utm.php, so adding mailcoach.app or flareapp.io later is a one-line change.

Surface	source	medium	campaign
Post page, listings, excerpts, RSS	freek.dev	referral	blogpost-{id}-{slug}
Community links page	freek.dev	referral	community-link-{id}-{slug}
Ads	freek.dev	banner	ad-{id}
Videos	freek.dev	referral	video-{id}-{slug}
Newsletter	newsletter	email	freek-dev-issue-{n}
Tweet / toot / Bluesky	twitter / mastodon / bluesky	social	blogpost-{id}-{slug}

Campaign identifies the content, source and medium identify the channel, so the same post is comparable across newsletter, social and the site.

UtmTagger tags at output time rather than baking parameters into the stored html column. That keeps the scheme changeable without re-rendering every post, and it needs no backfill. Existing query strings and fragments are preserved, and a URL that already carries a utm_source is left alone.

https://ohdear.app/docs?section=uptime#alerts
→ https://ohdear.app/docs?section=uptime&utm_source=freek.dev&utm_medium=referral&utm_campaign=blogpost-42-my-post#alerts

Canonical URLs, JSON-LD, og tags, the public API and Filament admin are deliberately left untagged.

Two things worth knowing:

• The newsletter archive renders campaign HTML stored from Mailcoach, so clicks from /newsletter/archive/* are attributed to utm_medium=email rather than to the web page. Low volume, left as is.
• Sponsor links pasted into Mailcoach after getMarkdown() runs are not swept.

194 tests pass.