No feedback is given on long running workflows

[Phu2]

Eg. using open-oaipmh on larger OAI endpoints. The workflow actually runs successfully but the progress icon still rotates forever.

[dr0i]

We would like to see a progress bar, but is there even a possibility to to that with open-oaipmh, i.e. is there any information? At least when using http-opener we won't have those numbers. But at least, after #210, we have a max time defined which we can show as a progress bar.