make rest controller more generic to support additional workflows

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #116
| License       | MIT
| Doc PR        | TODO

/cc @uwej711 

btw for the doc, this is using symfony http handling, meanign X-HTTP-Method-Override is supported as well. when documenting this we should make sure to explain the different ways to configure which workflows should be available (firewall, route, access checker).