polish(auth): Add allow list for new fxa mailer sending

Author: dschom

packages/fxa-auth-server/config/index.ts

@@ -597,12 +597,7 @@ const convictConf = convict({
       ignoreTemplates: {
         doc: 'Always ignore bounces from these email templates',
         format: Array,
-        default: [
-          'verifyLoginCode',
-          'verifyLogin',
-          'recovery',
-          'unblockCode',
-        ],
+        default: ['verifyLoginCode', 'verifyLogin', 'recovery', 'unblockCode'],
         env: 'BOUNCES_IGNORE_TEMPLATES',
       },
       deleteAccount: {
@@ -682,6 +677,12 @@ const convictConf = convict({
       default: true,
       env: 'SMTP_METRICS_ENABLED',
     },
+    fxaMailerDisableSend: {
+      doc: 'Array of templates that should not be supported by fxa mailer. Used to fallback to previous email sending if in a pinch.',
+      format: Array,
+      default: [''],
+      env: 'SMTP_FXA_MAILER_DISABLE_SEND',
+    },
   },
   maxEventLoopDelay: {
     doc: 'Max event-loop delay before which incoming requests are rejected',

packages/fxa-auth-server/lib/senders/fxa-mailer.ts

@@ -53,6 +53,19 @@ export class FxaMailer extends FxaEmailRenderer {
     super(bindings);
   }
 
+  /**
+   * Feature flag esque method that signals if the template is supported by the new mailer. Used to easily
+   * fall back to old email code if necessary.
+   * @param templateName The name of the template to check on.
+   * @returns True if the email can be sent, and false if the template is included in the SMTP_FXA_MAILER_DISABLE_SEND list.
+   */
+  canSend(templateName: string) {
+    if (this.mailerConfig.fxaMailerDisableSend.includes(templateName)) {
+      return false;
+    }
+    return true;
+  }
+
   async sendRecoveryEmail(
     opts: EmailSenderOpts &
       OmitCommonLinks<TemplateData> &