curl --request POST \
  --url https://{server}/api/projects/{project_pk}/members/ \
  --header 'Content-Type: application/json' \
  --cookie sessionid= \
  --data '
{
  "user_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a"
}
'

{
  "user": {
    "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "name": "<string>",
    "email": "jsmith@example.com"
  },
  "created_at": "2023-11-07T05:31:56Z"
}