curl --request POST \
  --url https://api.dfns.io/permissions/{permissionId}/assignments \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'X-DFNS-USERACTION: <api-key>' \
  --data '{
  "identityId": "<string>"
}'

{
  "id": "<string>",
  "permissionId": "<string>",
  "identityId": "<string>",
  "isImmutable": true,
  "dateCreated": "<string>",
  "dateUpdated": "<string>"
}