(Re-)Verify (un-) confirmed DOI's saved in dApp.

1. Display possible errors in special errors field (done) and remove it when error is resolved. (not done)
2. if there was no funding and a DOI is queuing or even already not queuing anymore it must be possible rerun this DOI-Request from the GUI.
3. If a DOI failed because of any error, it should be possible to delete the DOI completely from all tables. If it's already in the blockchain, further discussion would be needed here what is best in this case.

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