Validate an RCS card payload without creating anything (Flow Builder V2)
Thin wrapper around the same pure validation used by templates/create — runs every RCS card limit check (title/subtitle/body length, ≤4 buttons, per-type title length, URL/phone format) with NO database write and NO Twilio call, so a card-authoring UI can show inline errors on every keystroke. Authenticated workspace user (Bearer).
POST
https://api.channelautomation.com/api/rcs/workspaces/{workspaceId}/templates/validate