WhatsApp contacts using coexistence are identified by more than one
source ID (a phone `wa_id` and a `BR.`/BSUID identity), so a single
contact ends up owning multiple `contact_inbox` records. The "reopen the
same conversation" feature scoped conversation reuse to a single
`contact_inbox`, so messages arriving under a different identity of the
same contact started a brand-new conversation — even with reopen enabled
— producing duplicate conversations.
This scopes reuse to the contact across all of its `contact_inbox`
records in the inbox instead of a single `contact_inbox`.
## Closes
- [CW-7651
](https://linear.app/chatwoot/issue/CW-7651/duplicate-conversations)
## How to reproduce
1. On a WhatsApp Cloud inbox with "reopen the same conversation" (lock
to single conversation) enabled.
2. Have a coexistence contact whose webhooks alternate between carrying
the phone `wa_id` and only the BSUID identity.
3. Before: each identity opens its own conversation → duplicates. After:
incoming messages reopen the contact's existing conversation regardless
of which identity the webhook carried.
## What changed
- `Whatsapp::IncomingMessageBaseService#set_conversation` now looks up
reusable conversations via `@contact.conversations.where(inbox_id:
@inbox.id)` instead of `@contact_inbox.conversations`.
- Updated existing specs to wire the conversation's `contact` to the
contact_inbox's contact, mirroring production data.
