Rule-engine-based list endpoint — an alternative to the simple filter.* query params on the plain list endpoint, for building complex AND/OR filter conditions. This endpoint is served by a separate microservice from most of the API (not master_service), and its filter schema differs in two ways from other modules' generic-filter endpoints: each filter_rules entry also carries an explicit field_type, and the operator enum is wider (adds GREATER_THAN_EQUAL_TO, LESS_THAN_EQUAL_TO, IN). sort_by only accepts property_name or created_at — the smallest allow-list of any filter endpoint in the API (note: the service's own 400 validation message text says "created_by", but the actual accepted value is created_at — a mismatch in the error message itself, not in behavior). A filter_rules entry with key: "keyword" is pulled out and used as a free-text search instead of going through the rule engine.