Change from RESTEasy Classic to RESTEasy Reactive.

Change-Id: I3a3386c3a3a380b8217ac1667cc623625aeee532
diff --git a/src/main/java/eu/mulk/mulkcms2/benki/newsletter/NewsletterResource.java b/src/main/java/eu/mulk/mulkcms2/benki/newsletter/NewsletterResource.java
index cceddb1..5e8614f 100644
--- a/src/main/java/eu/mulk/mulkcms2/benki/newsletter/NewsletterResource.java
+++ b/src/main/java/eu/mulk/mulkcms2/benki/newsletter/NewsletterResource.java
@@ -5,6 +5,7 @@
 import io.quarkus.mailer.MailTemplate.MailTemplateInstance;
 import io.quarkus.qute.CheckedTemplate;
 import io.quarkus.qute.TemplateInstance;
+import io.smallrye.common.annotation.Blocking;
 import jakarta.transaction.Transactional;
 import jakarta.ws.rs.FormParam;
 import jakarta.ws.rs.GET;
@@ -17,6 +18,7 @@
 
 @Path("/newsletter")
 @Produces(TEXT_HTML)
+@Blocking
 public class NewsletterResource {
 
   @CheckedTemplate