Get a list of ResponsiblePartyInfo objects. These link a Party (individual or organisation) to
a principal record type (e.g. Observation, Instrument, Project) and the role which the Party was
undertaking. Additionally, the priority value indicates an ordering that may be present for
that given role for the relatedTo object.

GET /api/v3/rpis/?format=api&offset=180600
HTTP 200 OK
Allow: GET, POST, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "count": 180570,
    "next": null,
    "previous": "https://api.catalogue.ceda.ac.uk/api/v3/rpis/?format=api&limit=100&offset=180500",
    "results": []
}