JAMES-3498 Modify the access for CassandraEventDeadLetters, CassandraEventDeadLettersDAO

Make it public for easy create manually by constructor via Guice
diff --git a/event-bus/cassandra/src/main/java/org/apache/james/events/CassandraEventDeadLetters.java b/event-bus/cassandra/src/main/java/org/apache/james/events/CassandraEventDeadLetters.java
index 2a0828f..63699ac 100644
--- a/event-bus/cassandra/src/main/java/org/apache/james/events/CassandraEventDeadLetters.java
+++ b/event-bus/cassandra/src/main/java/org/apache/james/events/CassandraEventDeadLetters.java
@@ -32,8 +32,8 @@
     private final CassandraEventDeadLettersGroupDAO cassandraEventDeadLettersGroupDAO;
 
     @Inject
-    CassandraEventDeadLetters(CassandraEventDeadLettersDAO cassandraEventDeadLettersDAO,
-                              CassandraEventDeadLettersGroupDAO cassandraEventDeadLettersGroupDAO) {
+    public CassandraEventDeadLetters(CassandraEventDeadLettersDAO cassandraEventDeadLettersDAO,
+                                     CassandraEventDeadLettersGroupDAO cassandraEventDeadLettersGroupDAO) {
         this.cassandraEventDeadLettersDAO = cassandraEventDeadLettersDAO;
         this.cassandraEventDeadLettersGroupDAO = cassandraEventDeadLettersGroupDAO;
     }
diff --git a/event-bus/cassandra/src/main/java/org/apache/james/events/CassandraEventDeadLettersDAO.java b/event-bus/cassandra/src/main/java/org/apache/james/events/CassandraEventDeadLettersDAO.java
index a60e21b..4014caa 100644
--- a/event-bus/cassandra/src/main/java/org/apache/james/events/CassandraEventDeadLettersDAO.java
+++ b/event-bus/cassandra/src/main/java/org/apache/james/events/CassandraEventDeadLettersDAO.java
@@ -49,7 +49,7 @@
     private final PreparedStatement containEventsStatement;
 
     @Inject
-    CassandraEventDeadLettersDAO(CqlSession session, EventSerializer eventSerializer) {
+    public CassandraEventDeadLettersDAO(CqlSession session, EventSerializer eventSerializer) {
         this.executor = new CassandraAsyncExecutor(session);
         this.eventSerializer = eventSerializer;
         this.insertStatement = prepareInsertStatement(session);