POST
/actions/user/sequences/{sequence_id}/task-types/{task_type_id}/subscribe
curl \
--request POST 'http://api.example.com/actions/user/sequences/a24a6ea4-ce75-4665-a070-57453082c25/task-types/a24a6ea4-ce75-4665-a070-57453082c25/subscribe' \
--header "Authorization: $API_KEY"