[CORL-943] Send test emails (#2882)

* add smtp test email

* disable button if email not enabled

* add error handling

* internationalize strings

* sort imports

src/core/server/queue/tasks/mailer/templates/index.ts

@@ -3,6 +3,15 @@ interface EmailTemplate<T extends string, U extends {}> {
   context: U;
 }
 
+type TestContext<T extends string, U extends {}> = EmailTemplate<T, U>;
+
+export type SMTPTestTemplate = TestContext<
+  "test/smtp-test",
+  {
+    email: string;
+  }
+>;
+
 /**
  * NotificationContext
  */
@@ -203,6 +212,7 @@ type Templates =
   | OnFeaturedTemplate
   | DigestTemplate
   | OnCommentRejectedTemplate
+  | SMTPTestTemplate
   | OnCommentApprovedTemplate;
 
 export { Templates as EmailTemplate };

src/core/server/queue/tasks/mailer/templates/test/smtp-test.html

@@ -0,0 +1,8 @@
+{% extends "layouts/base.html" %} {% block content %}
+<div
+  data-l10n-id="email-template-testSmtpTest"
+  data-l10n-args="{{ context | dump }}"
+>
+  This is a test email sent to {{ context.email }}
+</div>
+{% endblock %}