Allow custom QLDB details from Docker

[basilesimon]

These details are presently hardcoded in src/qldb/index.ts:

export const Constants = {
  ledger_name: 'deptoolkit',
  doc_table_name: 'Document',
  doc_index_key: 'sku',
};

How would we pass these down from Docker, or from a configuration text file?

[basilesimon]

@pudo do I remember you using template literals (${...}) in Aleph or FTM?