Add authentication and auth scopes to application

[pretender91]

As a developer I want to invoke queries and mutations based on auth scope (guest, user, admin etc). Also I should have mutation to give auth token that grants me access to proper auth scope.

[pretender91]

After some research there are some theses:

Preferable scopes:

• Guest
• User
• Admin

As I understand we can put scopes in several places:

• in root (wide auth)
• in namespaces (aka put in root Query and Mutation)
• in types and fields.

I think we should put scopes as close as possible to root. Namespaces are preferable. Something like this:

enum Role {
    GUEST
    USER
    ADMIN
}

type Viewer {
    role: Role!
}

type Query {
    viewer: Viewer!
    guest: GuestQuery
    user: UserQuery
    admin: AdminQuery
}

type Mutation {
    guest: GuestMutation
    user: UserMutation
    admin: AdminMutation
}