Returns one adjustment in full: header, every line, the custom attributes of each, and the current status.

Takes either the adjustment id or the externalId supplied when it was created, and at least one is required. When both are sent the lookup filters on both, so a pair naming two different adjustments matches nothing and reports not found rather than quietly preferring one of them - a caller who keys their records on their own reference is told the two disagree instead of being handed the wrong adjustment.

Lookup values come back as their configured meanings rather than the stored codes, so a caller reads back the values they sent. Only adjustments belonging to the caller's own tenant can be read; another tenant's reports as not found rather than being acknowledged.