Define target user group in a workflow transition, with attendant notifications

[robbiejackson]

Current Limitation

Usually in workflow systems when you transition to a new stage you would be passing responsibility to a different team, and member(s) of that team would be notified when the work was transitioned to them. However, this functionality is not currently present.

Proposed Solution

Whenever you define a workflow you should be able (optionally) to associate with a Transition a target user group which will get notified whenever that transition is executed.

Whenever the transition is subsequently executed then it would be useful to provide some addiitional control over the notification. As a suggestion the following could be considered - these would be what the user executing the transition could choose:

1. Selecting one or more individual users from the user group instead of the whole group. (This would be relevant for example if you were returning the article to the user who had previously worked on it, to get him/her to do further work on it).
2. The ability to write a short text note which would be included in the notification
3. The ability to notify oneself as well - eg as a reminder of when you passed the work to the other team.

[HLeithner]

I got the info that @chmst is working on a notification plugin but one of our current limitation (also to reduce complexity) is that we don't have parameters in an article/item for workflow plugins, so we only have the options defined in the transition which would be a usergroup or of course a single user.

[chmst]

@robbiejackson I am working on it. Thank you for your engagment!

[bembelimen]

Closing as we're having a PR: #92