Replaces the content and mentions of one of the caller's replies; the reply keeps its reactions. Returns the updated record.

The record is looked up within the caller's tenant, and the caller must also be allowed to access the entity the email is linked to (employer, customer, lead, workflow or meeting, checked in that order); otherwise that entity's access check rejects the request. The caller also needs the update permission of the linked entity type (employers:write, leads:update, workflows:update, customers:update or meetings:update), checked in the service layer.

Errors: 400 if a mention is invalid; 403 if the reply belongs to another user or the update permission is missing; 404 if the record, the reply or a mentioned user does not exist.