title: Query status of active/hospitalized corda-flows
body: <p>I have a flow <code>MyFlow</code> that is invoked over RPC with some specific <code>args</code>, creates a tx putting some of the <code>args</code> in the output-state and then invokes <code>subFlow(FinalityFlow(...))</code>. Pretty standard I think. The RPC-client may invoke a bunch of those flows concurrently.
  Now if the notary or a receiving node is down, <code>MyFlow</code> may get suspended and retried.</p>
  
  <p>What I'd like to do now is to query/report to a user/node-operator the information about which transactions are currently "pending", i.e. being retried. Ideally I'd like to pull out the tx-id and the <code>args</code> of the unfinished instances of <code>MyFlow</code>. I can't seem to use <code>ProgressTracker</code>, since its <code>Steps</code> need to be defined up-front (i.e. in the Flow-constructor, where I don't know the tx-id yet), and the <code>label</code>-String anyway doesn't seem like a good carrier of structured data. <code>AuditService</code> looks like a good candidate since it has access to the steps <code>extraAuditData</code>, but it appears to only have the do-nothing <code>DummyAuditService</code> implementation, and I cannot hook a custom implementation without changing <code>AbstractNode.kt</code> (or can I ?).<br>
  Any ideas how this could be achieved ?</p>