Get a transaction by ID

Returns the transaction with enrichment fields: journalEntry (the single posted, non-deleted GL entry linked to the transaction and owned by its legal entity, with balanced debit/credit lines, or null), and matchedDocument (the matched receipt/bill owned by the transaction's legal entity, or null). When a linked entry or document is withheld, journalEntryUnavailableReason / matchedDocumentUnavailableReason says why (scope_mismatch: owned by another entity; ambiguous_posting: more than one posted entry links to the transaction); absent means nothing is linked. All other fields are unchanged.