resource types: add Instrument, Service and StudyRegistration

[carlinmack]

We currently support DataCite Metadata Schema 4.5 but we are missing resource types for:

• Instrument
• Service
• StudyRegistration

[tmorrell]

We're on DataCite 4.3...with additional resource types from 4.4. I think we should move to 4.6, but it would be good to do it more holistically than just adding recource types. Unless someone has a specific requirement for these types.

[carlinmack]

Ah apologies, from https://github.com/inveniosoftware/datacite I figured that we supported 4.5. Definitely agree about doing it holistically! We received a support ticket about wanting to publish a StudyRegistration type record