Complete base flow for TOTP setup

- Includes DB storage and code validation.
- Extracted TOTP work to its own service file.
- Still needs testing to cover this side of things.

database/migrations/2021_06_30_173111_create_mfa_values_table.php

@@ -0,0 +1,34 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+class CreateMfaValuesTable extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::create('mfa_values', function (Blueprint $table) {
+            $table->increments('id');
+            $table->integer('user_id')->index();
+            $table->string('method', 20)->index();
+            $table->text('value');
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::dropIfExists('mfa_values');
+    }
+}