This PR was merged into the 3.4 branch.Discussion----------[Workflow] Add transition completed event| Q             | A| ------------- | ---| Branch?       | 3.4| Bug fix?      | yes| New feature?  | yes| BC breaks?    | no| Deprecations? | no| Tests pass?   | yes| Fixed tickets | -| License       | MIT| Doc PR |symfony/symfony-docs#8213---Because the "entered" event is the only event dispatched after the new marking is applied, and publish's an event upon entering into a "Place" (as opposed to completing a transition), it is not sufficient for a lot of use cases and is causing bugs.Example:Enabled Transitions:1. A -> B2. B -> C3. C -> BTransition 1 and transition 3, will dispatch an "entered" event on Place B, forcing post transition behaviour to be the same for both transition 1 and 3.A user might need different behaviour depending on the transition, rather the the destination.A concrete use case would be when applying an "undo" transition to a subject. One may or may not want to re-trigger all the events associated with the original transition to that Place.I propose adding a "completed" event (ie. Transition completed) in addition to the entered event.Commits-------c254cac [Workflow] Added an transition completed event

…zzyp)This PR was submitted for the master branch but it was merged into the 3.4 branch instead (closes#8213).Discussion----------[Workflow] Document the new transition completed eventas per PR -symfony/symfony#22587Commits-------b8249ab [Workflow] Document the new transition completed event