Resolve a channel source to an end user (graph-backed)

curl --request POST \
  --url https://api-sandbox.featherhq.com/v1/identity/resolve \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "channel": "<string>",
  "external_id": "<string>",
  "org_external_end_user_id": "<string>"
}
'

{
  "end_user_id": "<string>",
  "org_id": "<string>",
  "is_new": true,
  "context_level": "<string>",
  "display_name": "<string>",
  "primary_email": "<string>",
  "primary_phone": "<string>",
  "org_external_end_user_id": "<string>"
}