Add Google Sign-In with templated HTML and env config

static/index.html

@@ -7,6 +7,7 @@
     <title>Tickets App</title>
     <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@awesome.me/webawesome@3/dist-cdn/styles/themes/default.css">
     <script type="module" src="https://cdn.jsdelivr.net/npm/@awesome.me/webawesome@3/dist-cdn/webawesome.loader.js"></script>
+    <script src="https://accounts.google.com/gsi/client" async></script>
     <style>
         body {
             font-family: var(--wa-font-sans);
@@ -20,7 +21,19 @@
     <wa-card>
         <h1 slot="header">Hello World</h1>
         <p>Welcome to the Tickets App!</p>
-        <wa-button variant="brand">Get Started</wa-button>
+        <div id="g_id_onload"
+            data-client_id="{{.GOOGLE_CLIENT_ID}}"
+            data-login_uri="/auth/google/callback"
+            data-auto_prompt="false">
+        </div>
+        <div class="g_id_signin"
+            data-type="standard"
+            data-size="large"
+            data-theme="outline"
+            data-text="sign_in_with"
+            data-shape="rectangular"
+            data-logo_alignment="left">
+        </div>
     </wa-card>
     <script type="module">
         window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', e => {