Change url from MDS to Fabrica new endpoint

[ntarocco]

The previous API url https://mds.datacite.org/ (https://doi.datacite.org/) will be removed. The new one should be: https://doi.datacite.org/.

See:

• https://blog.datacite.org/register-dois-with-the-new-fabrica-form/
• https://blog.datacite.org/fabrica-1-release/

[tmorrell]

This is a major API change and will require more than just swapping out the URL. I'm planning on wrapping the new API with new functions, but I don't have a specific schedule.

[tmorrell]

The new REST API has now been merged in and is available for use. The MDS interface is still available as DataCite had not depreciated it yet.