Admin configuration

RuniqueAppBuilder::new(config)
    .with_public_url("https://mysite.com")   // reset links sent from the admin
    .with_admin(|a| {
        a.site_title("My Administration")
         .routes(admins::routes("/admin"))
         // Custom dashboard (optional)
         .templates(|t| t.with_dashboard("admin/my_dashboard.html"))
         .with_state(admins::admin_state())
    })

// The admin signs in eihwaz_users accounts — there is no separate
// admin user model and nothing to implement.
//
// Sign-in: password checked first (same timing for any username),
// then the account must be active and is_staff or is_superuser.
let user = authenticate_admin(&db, &username, &password).await; // Option<Model>

// What a staff member may do on each resource comes from their groups
// (eihwaz_groupes / eihwaz_groupes_droits), read from the database on
// every request: removing a right takes effect immediately.
// A superuser passes every check.

// For each resource declared in admin!:
GET    /admin/                         -> dashboard
GET    /admin/article/list             -> list
GET    /admin/article/create           -> create form
POST   /admin/article/create           -> create handler
GET    /admin/article/{id}/detail      -> detail
GET    /admin/article/{id}/edit        -> edit form
POST   /admin/article/{id}/edit        -> edit handler
POST   /admin/article/{id}/delete      -> delete
POST   /admin/article/bulk             -> group actions

// Every write goes through the same gate: right on the resource,
// rows the account may touch, fields of the form only.