Honour opt-out replies on outbound WhatsApp campaigns

The problem A contact who replies "stop" / "unsubscribe" to a WhatsApp campaign keeps receiving the next one. Chatwoot has no concept of an opted-out contact — searching the codebase for opt_out returns nothing, and the only related matches for unsubscribe are webhook teardown for Instagram/Facebook/Twitter, not recipient opt-out. Why it matters commercially This is not a nicety. Meta's quality rating is computed from block reasons over a rolling 7-day window, and "Spam" / "Didn't sign up" are the two most damaging. Meta's own guidance is explicit: *provide a clear way to opt out in the message*. A business that keeps messaging someone who asked to stop gets its number rated down, then throttled, then disabled — and Chatwoot is the tool that sent those messages. For an operator running campaigns from Chatwoot today, the only workaround is to watch inbound replies by hand and remove contacts manually. That does not scale past a…