The university library of Technische Universität Berlin developed support for DOIs in DSpace.
The plan is to get it into the next release DSpace 4.0. The developers would be glad if anyone interested in this feature could test it. To test it, it would be helpful if you're familiar with installing DSpace using its source release.
They published their code on github and wrote some notes (https://wiki.duraspace.org/display/~pbecker/DOI+support+using+DataCite) that may help you testing and using it.
They would appreciate any comments in this ticket: https://jira.duraspace.org/browse/DS-1535.