Add an integration service to retrieve process instances according to the following criteria:
- process instance state: only process instances in the given state will be returned. Accepted state are: 'active', 'suspended', 'finished'. A process instance in state 'active' means that neither the process instance nor the corresponding process definition are suspended,
- process definition identifier, only process instances matching this process definition will be returned,
- process instance identifier, only process instance matching this process instance identifier will be returned.