Add an actor

A new person in the cast, with the first role they play (actor) and optionally that role's login: login: { email, password } hands over one you already seeded; login: 'tada' has Tada make it (planted through your app's own invite when Tada's admin is inside), its password on this answer once and never again. Refused when the environment is not open to test users. To give a role to an actor who is already in the cast, PUT /cast/{actor}/roles/{role}.