Subscribers API

GET /v1/subscribers?list_id=lst_abc
POST /v1/subscribers {email, list_id, first_name, tags}
GET /v1/subscribers/{id}
PATCH /v1/subscribers/{id}
DELETE /v1/subscribers/{id}
GET /v1/subscribers/search?email=jane@example.com
POST /v1/subscribers/{id}/unsubscribe