Individual transaction details from <TxDtls> within an entry details block.
Remittance information
remittance_info is one of:
{:unstructured, text}— free-text string (max 140 chars, from<Ustrd>){:structured, %{ref: ..., ref_type: ..., creditor_ref: ...}}— from<Strd>nil— no remittance info present
Related parties
related_parties is a map with optional keys:
:debtor, :debtor_account, :creditor, :creditor_account,
:ultimate_debtor, :ultimate_creditor, each being a %{name, iban, other_id} map.
Related agents
related_agents is a map with optional keys:
:debtor_agent, :creditor_agent, each being a %{bic, name} map.