feat: add OAuth-only self-registration setting

database/migrations/2024_01_01_000001_add_oauth_registration_settings.php

@@ -0,0 +1,22 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('instance_settings', function (Blueprint $table) {
+            $table->boolean('is_oauth_registration_enabled')->default(false)->after('is_registration_enabled');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('instance_settings', function (Blueprint $table) {
+            $table->dropColumn('is_oauth_registration_enabled');
+        });
+    }
+};