Optimized loading of page/chapter URLs to be a little more efficient

- Loaded book_slug as part of chapter/page queries instead of books
 being loaded in afterwards.
- Removed unused page method.
- Updated some page queries to load specific attributes.

app/Entities/Models/BookChild.php

@@ -10,14 +10,29 @@ use Illuminate\Database\Eloquent\Relations\BelongsTo;
  *
  * @property int  $book_id
  * @property int  $priority
+ * @property string  $book_slug
  * @property Book $book
  *
  * @method Builder whereSlugs(string $bookSlug, string $childSlug)
  */
 abstract class BookChild extends Entity
 {
+
+    protected static function boot()
+    {
+        parent::boot();
+
+        // Load book slugs onto these models by default during query-time
+        static::addGlobalScope('book_slug', function(Builder $builder) {
+            $builder->addSelect(['book_slug' => function($builder) {
+                $builder->select('slug')
+                    ->from('books')
+                    ->whereColumn('books.id', '=',  'book_id');
+            }]);
+        });
+    }
     /**
-     * Scope a query to find items where the the child has the given childSlug
+     * Scope a query to find items where the child has the given childSlug
      * where its parent has the bookSlug.
      */
     public function scopeWhereSlugs(Builder $query, string $bookSlug, string $childSlug)