Stream query workflows results out of rest api. (#382)

* Stream results out of rest api, lowering latency to first item. The main table query is still done synchronously, but additional queries are done on the stream lowering latency
* Performance is only lightly improved due to lower memory usage

nflow-rest-api-common/src/main/java/io/nflow/rest/v1/converter/ListWorkflowDefinitionConverter.java

@@ -37,9 +37,7 @@ public ListWorkflowDefinitionResponse convert(AbstractWorkflowDefinition<? exten
     }
     for (Entry<String, List<String>> entry : definition.getAllowedTransitions().entrySet()) {
       State state = states.get(entry.getKey());
-      for(String targetState : entry.getValue()) {
-        state.transitions.add(targetState);
-      }
+      state.transitions.addAll(entry.getValue());
     }
     for (Entry<String, WorkflowState> entry : definition.getFailureTransitions().entrySet()) {
       State state = states.get(entry.getKey());

nflow-rest-api-common/src/main/java/io/nflow/rest/v1/msg/ListWorkflowDefinitionResponse.java

@@ -64,7 +64,7 @@ public static class TransitionDelays extends ModelObject {
 
   }
 
-  public static class Signal {
+  public static class Signal extends ModelObject {
 
     @ApiModelProperty(value = "Signal value", required = true)
     public int value;