curl --request GET \
  --url https://api.{workspaceId}.clinia.cloud/mdm/v1/relationship-definitions/{relationshipDefinitionKey} \
  --header 'X-Clinia-API-Key: <api-key>'

{
  "from": "<string>",
  "to": "<string>",
  "relationshipMapping": {},
  "key": "<string>"
}