Achievement approving authority

The authority for approving achievement can only be a single org. Achievement verification becomes difficult for multi-body events.

Authority for approving achievement can be expanded to have a list of organisations.

Start by tracing how achievement approval authority is represented and how the verification flow checks it. Define the multi-organisation behavior from the issue, then confirm that achievements for multi-body events can be approved and verified by the listed organisations.

Written by the indexing model from the issue text.