add pivot loaded bool methods (#46555)

src/Illuminate/Http/Resources/ConditionallyLoadsAttributes.php

@@ -329,13 +329,36 @@ protected function whenPivotLoadedAs($accessor, $table, $value, $default = null)
         }
 
         return $this->when(
-            isset($this->resource->$accessor) &&
-            ($this->resource->$accessor instanceof $table ||
-            $this->resource->$accessor->getTable() === $table),
+            $this->hasPivotLoadedAs($accessor, $table),
             ...[$value, $default]
         );
     }
 
+    /**
+     * Determine if the resource has the specified pivot table loaded.
+     *
+     * @param  string  $table
+     * @return bool
+     */
+    protected function hasPivotLoaded($table)
+    {
+        return $this->hasPivotLoadedAs('pivot', $table);
+    }
+
+    /**
+     * Determine if the resource has the specified pivot table loaded with a custom accessor.
+     *
+     * @param  string  $accessor
+     * @param  string  $table
+     * @return bool
+     */
+    protected function hasPivotLoadedAs($accessor, $table)
+    {
+        return isset($this->resource->$accessor) &&
+            ($this->resource->$accessor instanceof $table ||
+            $this->resource->$accessor->getTable() === $table);
+    }
+
     /**
      * Transform the given value if it is present.
      *