Add new endpoint to allow status of lettings applicant guarantor to be updated

[plittlewood-rpt]

Background context Logged from research in #3829

To support the availability of tenant guarantor functionality in AgencyCloud, we should provide the capability to update the status of a guarantor associated to lettings applicants, which is often done prior to a tenancy agreement being put in place

Specification

• Project: Reapit.Services.Applicants
• Add new PATCH /applicants/{id}/guarantors/{contactId}/[guarantorContactId} endpoint, that allows a relationship between a lettings applicant and their guarantor(s) to be updated

UpdateApplicantGuarantorModel

{
    "status": "" -- appliedFor/received/notApplied
}

Validations

• New endpoint should be protected with the applicants.write scope
• status should always be provided
• status should be one of allowed values (use enum) when provided (maps to extra.extra.refStatus)
• Action should not be permitted on an archived resource

[cduggan-reapit]

The endpoints exposing this functionality have been created, but are disabled using the [NonAction] attribute and the tests are skipped while we decide whether guarantors/references should be read-only. I'm unassigning myself and moving the ticket back to to-do for now.