add smtp module and testing

app/templates/config.html

@@ -33,6 +33,14 @@
   <div class="notice">{{ ticktick_oauth_notice }}</div>
   {% endif %}
 
+  {% if smtp_test_error %}
+  <div class="alert">{{ smtp_test_error }}</div>
+  {% endif %}
+
+  {% if smtp_test_notice %}
+  <div class="notice">{{ smtp_test_notice }}</div>
+  {% endif %}
+
   <div class="meta single-column">
     <div>
       <dt>当前用户</dt>
@@ -102,6 +110,20 @@
           {% endif %}
         </div>
         {% endif %}
+
+        {% if section.name == "SMTP" %}
+        <div class="integration-action-row">
+          <div>
+            <p class="integration-action-title">SMTP Test Email</p>
+            <p class="integration-action-copy">Save the SMTP settings first, then send a simple plaintext test email to the configured recipient.</p>
+          </div>
+          {% if smtp_test_ready %}
+          <button type="submit" formaction="/config/smtp/test" formmethod="post">Send SMTP Test</button>
+          {% else %}
+          <span class="button-link disabled" aria-disabled="true">Send SMTP Test</span>
+          {% endif %}
+        </div>
+        {% endif %}
       </fieldset>
       {% endfor %}