DataCite events shoudl use EPrints::DataObj::EventQueue->create_unique

[drn05r]

The following lines use create_dataobj, when they should use create_unique. This would save multiple instances of the same task being created:

DataCiteDoi/lib/plugins/EPrints/Plugin/Event/DataCiteEvent.pm

Lines 287 to 291 in bbd1166

	$repo->dataset( "event_queue" )->create_dataobj({
	pluginid => "Event::DataCiteEvent",
	action => "datacite_doi",
	params => [ $dataobj->internal_uri, $dataobj_doi ],
	});

DataCiteDoi/lib/plugins/EPrints/Plugin/Event/DataCiteEvent.pm

Lines 322 to 326 in bbd1166

	$repo->dataset( "event_queue" )->create_dataobj({
	pluginid => "Event::DataCiteEvent",
	action => "datacite_doi",
	params => [ $dataobj->internal_uri, $dataobj_doi ],
	});

DataCiteDoi/lib/plugins/EPrints/Plugin/Event/DataCiteEvent.pm

Lines 432 to 437 in bbd1166

	$dc = $datacite_ds->create_dataobj(
	{
	datasetid => $class,
	objectid => $dataobj->id
	}
	);

Also, they will benefit from the web (i..e user) request prioritisation of event queue tasks in eprints/eprints3.4#581 coming in EPrints v3.4.8.

Change should just be a simple replacement of create_dataobj with create_unique.