Merge current features with security hardening and automatic safe initialization

src/lib/mail.ts

@@ -9,6 +9,7 @@ type SendAppEmailInput = {
   react: ReactNode;
   from?: string;
   replyTo?: string | string[];
+  idempotencyKey?: string;
 };
 
 type SendAppEmailResult =
@@ -36,6 +37,7 @@ export async function sendAppEmail({
   react,
   from = process.env.EMAIL_FROM,
   replyTo,
+  idempotencyKey,
 }: SendAppEmailInput): Promise<SendAppEmailResult> {
   if (Array.isArray(to)) {
     let id: string | undefined;
@@ -72,13 +74,16 @@ export async function sendAppEmail({
 
   try {
     resendClient ??= new Resend(process.env.RESEND_API_KEY);
-    const { data, error } = await resendClient.emails.send({
-      from: from!,
-      to,
-      subject,
-      react,
-      replyTo,
-    });
+    const { data, error } = await resendClient.emails.send(
+      {
+        from: from!,
+        to,
+        subject,
+        react,
+        replyTo,
+      },
+      { idempotencyKey },
+    );
 
     if (error) {
       console.error("Resend konnte die E-Mail nicht versenden:", error);