Retrieves complete details of a specific accounting event.

This endpoint provides all information about an individual accounting event,
including its nature, associated contracts, financial details, and all related
accounting transactions and entries.

The response includes:

• Event metadata (nature, processed_at, amount_received_in_cents)
• Related contract and asset references
• Full accounting transactions with their entries (effective_date, description, nature, journal)
• A flat list of all accounting entries for convenience

Each accounting entry includes denormalized fields from its parent transaction
(accounting_transaction_nature, accounting_transaction_description, accounting_transaction_effective_date).