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 
thats the point: the methods define the workflow, so if we register custom workflows with RestService, we need to accept any method. the RestService looks at the method and raises an error if there is no workflow for that method.

this is kind of the catchall for this url.