feat: ✨ Create LegacySettingsMigration to centralize migration methods

app/Classes/LegacySettingsMigration.php

@@ -0,0 +1,58 @@
+<?php
+
+namespace App\Classes;
+
+use Exception;
+use Illuminate\Support\Facades\DB;
+use Spatie\LaravelSettings\Migrations\SettingsMigration;
+
+
+abstract class LegacySettingsMigration extends SettingsMigration
+{
+    public function getNewValue(string $name)
+    {
+        $new_value = DB::table('settings')->where([['group', '=', 'general'], ['name', '=', $name]])->get(['payload'])->first();
+
+        // Some keys returns '""' as a value.
+        if ($new_value->payload === '""') {
+            return null;
+        }
+
+        // remove the quotes from the string
+        if (substr($new_value->payload, 0, 1) === '"' && substr($new_value->payload, -1) === '"') {
+            return substr($new_value->payload, 1, -1);
+        }
+
+        return $new_value->payload;
+    }
+
+    /**
+     * Get the old value from the settings_old table.
+     * @param string $key The key to get the value from table.
+     * @param int|string|bool|null $default The default value to return if the value is null. If value is not nullable, a default must be provided.
+     */
+    public function getOldValue(string $key,  int|string|bool|null $default = null)
+    {
+        $old_value = DB::table('settings_old')->where('key', '=', $key)->get(['value', 'type'])->first();
+
+        if (is_null($old_value->value)) {
+            return $default;
+        }
+
+        switch ($old_value->type) {
+            case 'string':
+            case 'text':
+                // Edgecase: The value is a boolean, but it's stored as a string.
+                if ($old_value->value === "false" || $old_value->value === "true") {
+                    return filter_var($old_value->value, FILTER_VALIDATE_BOOL);
+                }
+                return $old_value->value;
+            case 'boolean':
+                return filter_var($old_value->value, FILTER_VALIDATE_BOOL);
+            case 'integer':
+                return filter_var($old_value->value, FILTER_VALIDATE_INT);
+            default:
+                throw new Exception("Unknown type: {$old_value->type}");
+        }
+    }
+}