Inject plainRestTemplate into SubmitContactUseCaseImpl and update RestTemplateConfig.

backend/server/src/main/java/dev/rheinsw/server/contact/usecase/SubmitContactUseCaseImpl.java

@@ -8,9 +8,12 @@ import dev.rheinsw.server.mail.domain.MailRequest;
 import dev.rheinsw.server.mail.usecase.SendMailUseCase;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.stereotype.Service;
+import org.springframework.web.client.RestTemplate;
 
 import java.time.LocalDateTime;
 
@@ -27,6 +30,10 @@ public class SubmitContactUseCaseImpl implements SubmitContactUseCase {
     private final ContactRequestsRepo contactRepository;
     private final SendMailUseCase sendMailUseCase;  // Inject SendMailUseCase
 
+    @Autowired
+    @Qualifier("plainRestTemplate")
+    private RestTemplate restTemplate;
+
     public SubmitContactUseCaseImpl(HCaptchaValidator captchaValidator,
                                     ContactRequestsRepo contactRepository,
                                     SendMailUseCase sendMailUseCase) {