Implement backend for contact form with gateway integration

backend/common/src/main/java/dev/rheinsw/shared/mail/MailServiceClient.java

@@ -25,9 +25,6 @@ public class MailServiceClient {
 
     private static final String MAIL_ENDPOINT = "http://gateway/api/mail";
 
-    @Value("${INTERNAL_API_KEY}")
-    private String internalApiKey;
-
     @Async
     public void sendMail(String email, String subject, String userMessage) {
         MailRequest request = new MailRequest(email, subject, userMessage);
@@ -37,7 +34,6 @@ public class MailServiceClient {
     private void postEmail(MailRequest request) {
         try {
             HttpHeaders headers = new HttpHeaders();
-            headers.set("X-Internal-Auth", internalApiKey);
 
             HttpEntity<MailRequest> entity = new HttpEntity<>(request, headers);