/v1/currentaccounts/{id}/documents had no handler at all -- the
account's own /v1/currentaccounts resource matches the request path
first and has no documents method, so it never fell through to the
generic /v1/{entityType}/{entityId}/documents resource that every
other entity type relies on. Current accounts got a 404 on every
Documents-tab request.
Delegates straight to the existing DocumentApiResource so current
accounts get identical behaviour to clients, loans, etc.