Creates a draft or ready message inside a campaign owned by the user, optionally attaching include and exclude audience tags.

Returns a responsive, table-based HTML email layout with placeholders (title, preview, body, cta_label, cta_url) and optional brand color — use as a starting "graphic" template for campaigns.

Lists newsletter campaigns: all campaigns for managers/administrators; only campaigns created by the user for editors (id, name, slug, description).

Returns newsletter delivery statistics for a date range: optional campaign filter, summary totals, per-message breakdown, and daily send timeseries.

Combines the newsletter report with short textual highlights (totals, best-performing message by sends) for quick interpretation.

Summarizes subscriber counts by status and lists tags with the most subscribers for audience planning.