Make the model:prune command easier to extend (#43919)

* Split up model pruning to a separate method

This improves the experience when extending/overwriting the prune command.

* Make typehinting less strict on the prune command

The `getDefaultPath()` method can also give back a list of paths for it to still work. This commit will reflect that in the PHPDocs of the method.

* Fix codestyle

src/Illuminate/Database/Console/PruneCommand.php

@@ -71,22 +71,33 @@ public function handle(Dispatcher $events)
         });
 
         $models->each(function ($model) {
-            $instance = new $model;
+            $this->pruneModel($model);
+        });
+
+        $events->forget(ModelsPruned::class);
+    }
 
-            $chunkSize = property_exists($instance, 'prunableChunkSize')
-                            ? $instance->prunableChunkSize
-                            : $this->option('chunk');
+    /**
+     * Prune the given model.
+     *
+     * @param  string  $model
+     * @return void
+     */
+    protected function pruneModel(string $model)
+    {
+        $instance = new $model;
 
-            $total = $this->isPrunable($model)
-                        ? $instance->pruneAll($chunkSize)
-                        : 0;
+        $chunkSize = property_exists($instance, 'prunableChunkSize')
+            ? $instance->prunableChunkSize
+            : $this->option('chunk');
 
-            if ($total == 0) {
-                $this->components->info("No prunable [$model] records found.");
-            }
-        });
+        $total = $this->isPrunable($model)
+            ? $instance->pruneAll($chunkSize)
+            : 0;
 
-        $events->forget(ModelsPruned::class);
+        if ($total == 0) {
+            $this->components->info("No prunable [$model] records found.");
+        }
     }
 
     /**
@@ -131,7 +142,7 @@ protected function models()
     /**
      * Get the default path where models are located.
      *
-     * @return string
+     * @return string|string[]
      */
     protected function getDefaultPath()
     {