Motivation:

OAI-PMH, by itself, doesn't identify the nature of the resource; rather,
this is achieved by the metadata record itself.

Just to mention it, OAI-PMH sets don't provide any guaranteed semantics;
such semantics can be added through the set description, but there's no
consensus or practice in doing this.

Therefore, in order to categorise OAI-PMH items by type, we need to
obtain records: listing identifiers isn't sufficient.  Moreover, Dublin
Core (as used currently) doesn't support the fine-grain type semantics
we would like present.

The DataCite metadata schema provides `resourceType` metadata, with the
`resourceTypeGeneral` providing the course-grain type of the resource.
This is what we would like to use.

Modification:

Add support for querying all records using the DataCite records.  This
task is very similar to the existing code that lists all identifiers of
records with Dublin Core.

The patch adds support for querying DataCite metadata as mostly a
copy-and-paste of the existing code.  This is technical debt that future
patches MUST address, through refactorinng.

The OAI-PMH client code is updated to support ListRecords requests.
This is also a copy-n-paste, inducing further technical debt that future
patches must address.

Result:

The facilities YAML file now includes a breakdown of OAI-PMH items based
on their DataCite resourceTypeGeneral.