Upsert contact

curl --request POST \
  --url https://api.openint.dev/v0/unified/crm/contact/_upsert \
  --header 'Content-Type: application/json' \
  --header 'x-apikey: <api-key>' \
  --header 'x-connection-id: <api-key>' \
  --data '{
  "upsert_on": {
    "key": "email",
    "values": [
      "<string>"
    ]
  },
  "record": {
    "first_name": "<string>",
    "last_name": "<string>",
    "email": "<string>",
    "phone": "<string>",
    "passthrough_fields": {}
  }
}'

{
  "record": {
    "id": "<string>",
    "updated_at": "<string>",
    "raw_data": {},
    "first_name": "<string>",
    "last_name": "<string>",
    "email": "<string>",
    "phone": "<string>"
  }
}