On your people controller, you can use the user-permissions's add service.
Example how to create an user by using service:
let user = await strapi.plugins['users-permissions'].services.user.add({
blocked: false,
confirmed: true,
username: 'new_username',
email: 'test@testemail.com',
password: 'secretpassword', //will be hashed automatically
provider: 'local', //provider
created_by: 1, //user admin id
updated_by: 1, //user admin id
role: 1 //role id
});
Where the user will contain the created id. You can use that id to create the people entity:
await strapi.services.people.create({
//people data here
// ...
users_permissions_user: user.id //map relation with the user
});