DB: Started update of entity loading to avoid global selects

Removes page/chpater addSelect global query, to load book slug, and
instead extracts base queries to be managed in new static class, while
updating specific entitiy relation loading to use our more efficient
MixedEntityListLoader where appropriate.

Related to #4823

app/Entities/Tools/MixedEntityListLoader.php

@@ -26,7 +26,7 @@ class MixedEntityListLoader
      * This will look for a model id and type via 'name_id' and 'name_type'.
      * @param Model[] $relations
      */
-    public function loadIntoRelations(array $relations, string $relationName): void
+    public function loadIntoRelations(array $relations, string $relationName, bool $loadParents): void
     {
         $idsByType = [];
         foreach ($relations as $relation) {
@@ -40,7 +40,7 @@ class MixedEntityListLoader
             $idsByType[$type][] = $id;
         }
 
-        $modelMap = $this->idsByTypeToModelMap($idsByType);
+        $modelMap = $this->idsByTypeToModelMap($idsByType, $loadParents);
 
         foreach ($relations as $relation) {
             $type = $relation->getAttribute($relationName . '_type');
@@ -56,7 +56,7 @@ class MixedEntityListLoader
      * @param array<string, int[]> $idsByType
      * @return array<string, array<int, Model>>
      */
-    protected function idsByTypeToModelMap(array $idsByType): array
+    protected function idsByTypeToModelMap(array $idsByType, bool $eagerLoadParents): array
     {
         $modelMap = [];
 
@@ -67,10 +67,10 @@ class MixedEntityListLoader
 
             $instance = $this->entityProvider->get($type);
             $models = $instance->newQuery()
-                ->select($this->listAttributes[$type])
+                ->select(array_merge($this->listAttributes[$type], $this->getSubSelectsForQuery($type)))
                 ->scopes('visible')
                 ->whereIn('id', $ids)
-                ->with($this->getRelationsToEagerLoad($type))
+                ->with($eagerLoadParents ? $this->getRelationsToEagerLoad($type) : [])
                 ->get();
 
             if (count($models) > 0) {
@@ -100,4 +100,19 @@ class MixedEntityListLoader
 
         return $toLoad;
     }
+
+    protected function getSubSelectsForQuery(string $type): array
+    {
+        $subSelects = [];
+
+        if ($type === 'chapter' || $type === 'page') {
+            $subSelects['book_slug'] = function ($builder) {
+                $builder->select('slug')
+                    ->from('books')
+                    ->whereColumn('books.id', '=', 'book_id');
+            };
+        }
+
+        return $subSelects;
+    }
 }