Refactor WebAPI Workflow

[joschrew]

In the last sprint I refactored the workspace Part of the API. Mongodb was added to store information about a workspace in the database. For the workflow-part the mongodb should also be used to store information about jobs and to be able to send a job-status to the user. Overview about things to be done in this "refactoring":

• use mongodb for jobs (and possibly for workflow-scripts)
• refactor "run_workflow" to "better" fit to the specification
• add GET /workflow/{workflow_id}/{job_id}. Therefore the mongdb is needed
• fix (some) open tasks mentioned in the source-code and some open issues related to the workflow
• revise the tests to fit the other mentioned changes
• the outcome of this task should be an available test-server with which it is possible to upload a workspace and a workflow and run the workflow on the workspace

[joschrew]

Status:

• code-refactoring finished for now
• the service is available in gönet (e.g. curl 141.5.99.53:5050/workspace). Since it would be possible to upload any nextflow-script and run it, I don't want to make it publicly available
• currently no processors except ocrd-dummy are available or useable. So running workflows is quite useless currently
• I don't know yet how to do the setup (regarding the processors), how to make the processors available. I would try to find that out in the next sprint: https://github.com/OCR-D/zenhub/issues/128