Allow scope() to be used for operations

[bparise]

I want to scope() records through hooks. I use scopes frequently in my API to allow users with certain roles access to mutate objects. I know I can just where={}, but scopes are way more convenient and centralized to the model.

Would be nice to:

hook => {
  hook.params.sequelize.scope = 'approved'
  return Promise.resolve(hook)
}

Right now, this setting is ignored because you have to scope records like:

Model.scope('approved').findAll()...

I can do a PR for this, just let me know!

let Model = this.Model
if (params.scope) {
  Model = this.Model.scope(params.scope)
}

[DesignByOnyx]

@bparise - If you want to submit a PR. I will endorse it. This would be a great feature! If you don't have time I will try and squeeze it in - let me know. If you want to do it, make sure to write tests and update the docs. You go to a particular page at https://docs.feathersjs.com/, then click the "Edit this page" link in the top.

[bparise]

Done! I'll update the documentation once the PR is officially accepted.

[daffl]

Closed via #142