Nightly UTM Taxonomy Audit from BigQuery Click Logs

Runs once a night against your BigQuery click/event table, validates every `utm_source`, `utm_medium`, `utm_campaign`, and `utm_content` value against your approved taxonomy (allowed sources, lowercase-kebab campaigns, no spaces), and produces a digest of malformed links ranked by click volume so the worst offenders surface first.

Use it when marketing data lands in a warehouse and dirty UTMs are quietly corrupting attribution. A nightly cadence catches yesterday's launches before weekly reporting runs, without anyone manually eyeballing campaign URLs.

1. 1A nightly schedule fires the workflow.
2. 2A BigQuery query pulls the prior day's distinct UTM combinations plus their click counts.
3. 3A validation step checks each combination against the taxonomy rules (allowlisted source/medium, casing, forbidden characters) and tags each as clean or malformed.
4. 4A branch ends the run quietly if zero violations exist.
5. 5Otherwise a formatting step builds a ranked offender table.
6. 6The report is posted to a marketing-ops Slack channel with the count and top offenders.