message: indexer-service: Fix database connection timeouts
  The trick is to wait for transactions to finish instead
  of potentially creating as many in parallel as there are
  active receipts with changes to be flushed.
diff: @@ -282,7 +282,7 @@ export class ReceiptManager {
  try {
  // Put this in a transaction because this has a write which is
  // dependent on a read and must be atomic or payments could be dropped.
  - this._sequelize.transaction(
  + await this._sequelize.transaction(
  { isolationLevel: Transaction.ISOLATION_LEVELS.REPEATABLE_READ },
  async (transaction: Transaction) => {
  const [state, isNew] = await this._receiptModel.findOrBuild({
  @@ -311,7 +311,7 @@ export class ReceiptManager {
  state.set('signature', receipt.signature)
  // Save the new or updated receipt to the db
  - await state.save()
  + await state.save({ transaction })
  },
  )
  } catch (e) {
  