curl --request POST \
  --url https://api.virtuoussoftware.com/api/Relationship \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "contactId": "<integer>",
  "relationshipType": "<string>",
  "contactIndividualId": "<integer>",
  "relatedContactId": "<integer>",
  "relatedContactIndividualId": "<integer>",
  "notes": "<string>"
}
'

{
  "id": "<integer>",
  "contactId": "<integer>",
  "contact": "<string>",
  "contactIndividual": "<string>",
  "relatedContactId": "<integer>",
  "relatedContact": "<string>",
  "relatedContactIndividual": "<string>",
  "relationshipType": "<string>",
  "notes": "<string>",
  "relatedContactViewUrl": "<string>"
}