[oauth] start oauth auth_code server implementation

layouts/modal.vue

@@ -0,0 +1,12 @@
+<template lang='pug'>
+  el-container
+    el-header
+    el-row(:gutter='20')
+      el-col(:span='12' :offset='6')
+        el-card.mt-5
+          h4(slot='header') <img src='/favicon.ico'/> {{$route.name}}
+          nuxt
+</template>
+<style lang="less">
+@import '../assets/style.less';
+</style>