Partial Update Intercompany Journal Entry

    Performs a partial update of an intercompany journal entry, allowing modification of specific fields without replacing the entire entry.

    This endpoint supports partial updates to:
    - Journal entry metadata (memo, date, currency, reference number)
    - Individual transaction modifications
    - Entity exchange rate adjustments
    - Vendor, department, and tag assignments
    - Account categorizations and amounts

    Key differences from PUT:
    - Only specified fields are updated (vs. full replacement)
    - Maintains existing data for unspecified fields
    - Supports granular transaction modifications
    - Preserves audit trail and timestamps
    - Allows incremental changes without full transaction rebuilds

    Validation requirements:
    - Modified transactions must maintain entity balance (debits = credits)
    - Cannot modify entries in closed accounting periods
    - All referenced accounts, vendors, departments must be active
    - Exchange rates must be valid for multi-currency transactions
    - Account assignments must be appropriate for transaction types