Move CMS-related entities into a “cms” package.

Change-Id: Ie350230552fa6f970f26412b40974ca4af7a9260
diff --git a/src/main/java/eu/mulk/mulkcms2/cms/comments/UsedTransactionKey.java b/src/main/java/eu/mulk/mulkcms2/cms/comments/UsedTransactionKey.java
new file mode 100644
index 0000000..57dd112
--- /dev/null
+++ b/src/main/java/eu/mulk/mulkcms2/cms/comments/UsedTransactionKey.java
@@ -0,0 +1,16 @@
+package eu.mulk.mulkcms2.cms.comments;
+
+import io.quarkus.hibernate.orm.panache.PanacheEntityBase;
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.Id;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "used_transaction_keys", schema = "public", catalog = "mulkcms")
+public class UsedTransactionKey extends PanacheEntityBase {
+
+  @Id
+  @Column(name = "key", nullable = false)
+  public long key;
+}