Multi-touch attribution model implemented — not exclusively last-click

Pure last-click attribution credits 100% of every conversion to whichever email the contact happened to click immediately before purchasing, ignoring the nurture sequence, re-engagement email, and product-update announcement that actually moved them down the funnel. Finance then starves the campaigns doing the real work, marketing kills the sequences that compound over weeks, and the attribution table cannot answer basic retrospective questions like "which first-touch emails drive the highest LTV cohorts." Full touchpoint storage is the prerequisite for every other model.

Record every email interaction into an attribution_touchpoints table keyed on (contact_id, campaign_id, event_type, occurred_at), then on conversion run an attribution query over a 30-day window that distributes credit across all touchpoints using a linear, time-decay, or position-based model. Store the credit distribution in a conversion_credits join table so reports can switch models without re-running ETL.

const creditPerTouchpoint = 1.0 / touchpoints.length