Steps to reproduce

• Synchronize a course with synchronized course parts
• You get a ClassCastException:

  java.lang.ClassCastException: class org.ametys.odf.coursepart.CoursePart cannot be cast to class org.ametys.odf.ProgramItem (org.ametys.odf.coursepart.CoursePart and org.ametys.odf.ProgramItem are in unnamed module of loader org.apache.catalina.loader.ParallelWebappClassLoader @54d18072)
  	at org.ametys.plugins.odfsync.apogee.scc.ApogeeSynchronizableContentsCollectionHelper.synchronizeContent(ApogeeSynchronizableContentsCollectionHelper.java:116)
  	at org.ametys.plugins.odfsync.apogee.scc.AbstractApogeeSynchronizableContentsCollection._synchronizeChildren(AbstractApogeeSynchronizableContentsCollection.java:921)
  	at org.ametys.plugins.odfsync.apogee.scc.impl.CourseSynchronizableContentsCollection.getAdditionalAttributeValues(CourseSynchronizableContentsCollection.java:83)
  	at org.ametys.plugins.contentio.synchronize.AbstractSimpleSynchronizableContentsCollection._fillContent(AbstractSimpleSynchronizableContentsCollection.java:412)
  	at org.ametys.plugins.contentio.synchronize.AbstractSimpleSynchronizableContentsCollection._synchronizeContent(AbstractSimpleSynchronizableContentsCollection.java:221)
  	at org.ametys.plugins.odfsync.apogee.scc.AbstractApogeeSynchronizableContentsCollection._synchronizeContent(AbstractApogeeSynchronizableContentsCollection.java:811)
  [...]