Add api sugar for mono gets mono

- While this doesn't change underlying behaviour, add sendEventCollect
  method which takes a mono and returns a mono as list of results.
- Add some notes to docs why this is like this, aka having regions
  returns multiple results.
- Fixes #922

docs/src/reference/asciidoc/appendix-reactormigration-communicating.adoc

@@ -12,7 +12,9 @@ include::samples/DocsMigrationTests.java[tags=snippetA]
 We're now solely working on a spring `Message` and reactor `Mono` and `Flux` classes.
 You can send a `Mono` of a `Message` and receive back a `Flux` of `StateMachineEventResult`.
 Remember that nothing happens until you subscribe to this `Flux`. More about
-this returned value, see <<sm-triggers-statemachineeventresult>>.
+this returned value, see <<sm-triggers-statemachineeventresult>>. Method `sendEventCollect`
+is just a syntactic sugar to pass in a `Mono` and get a `Mono` which wraps
+results as a list.
 
 ====
 [source,java,indent=0]

docs/src/reference/asciidoc/sm-triggers.adoc

@@ -20,6 +20,20 @@ include::samples/DocsConfigurationSampleTests.java[tags=snippetO]
 ----
 ====
 
+Whether you send one event or multiple events, result is always a sequence
+of results. This is so because in a presence multiple reqions, results will
+come back from multiple machines in those regions. This is shown
+with method `sendEventCollect` which gives a list of results. Method
+itself is a just a syntactic sugar collecting `Flux` as list. If there is
+just one region, this list contains one result.
+
+====
+[source,java,indent=0]
+----
+include::samples/DocsConfigurationSampleTests.java[tags=snippetO3]
+----
+====
+
 IMPORTANT: Nothing happens until returned flux is subscribed. See more about it from
 <<sm-triggers-statemachineeventresult>>.