New `associatedEntities` object in `thread.action` object

[bob983]

Threads contain action object which now contains a fresh new associatedEntities that can list IDs of entities associated with the action/thread.

...
"associatedEntities" : {
   "user" : 123,
   "workflow" : 345
}
...

All fields are optional and at the moment just those two are supported (and so far just one of the will be filled and only for some actions).