added username for uniqueness of connection db entry

backend/src/main/java/com/vaessl/app/connection/HomeboxEntity.java

@@ -25,6 +25,7 @@ public class HomeboxEntity extends ConnectionEntity {
         HomeboxEntity he = new HomeboxEntity();
 
         he.setAppUrl(request.appUrl());
+        he.setUsername(request.credentials().get("username"));
         he.setToken(response.token());
         he.setAttachmentToken(response.getExtraVar("attachmentToken"));
         he.setExpiresAt(response.expiresAt());