Add Calendar Event Management Service

- Introduce CalendarEventService interface for managing calendar events programmatically.
- Implement CalendarEventServiceImpl to provide methods for adding, updating, deleting, and retrieving calendar events.
- Ensure validation for required fields and implement event filtering by user and date range.
- Integrate with CalendarEventsFacade for database operations related to calendar events.

Author: jameswong3388

src/main/java/org/example/hvvs/model/CalendarEventsFacade.java

@@ -7,6 +7,8 @@
 import jakarta.ejb.Stateless;
 import jakarta.persistence.EntityManager;
 import jakarta.persistence.PersistenceContext;
+import jakarta.persistence.TypedQuery;
+import java.util.List;
 
 /**
  *
@@ -27,4 +29,28 @@ public CalendarEventsFacade() {
         super(CalendarEvents.class);
     }
 
+    /**
+     * Executes a named query with a single parameter
+     * 
+     * @param queryName the name of the named query
+     * @param paramName the parameter name
+     * @param paramValue the parameter value
+     * @return list of calendar events matching the query
+     */
+    public List<CalendarEvents> findByNamedQuery(String queryName, String paramName, Object paramValue) {
+        TypedQuery<CalendarEvents> query = em.createNamedQuery(queryName, CalendarEvents.class);
+        query.setParameter(paramName, paramValue);
+        return query.getResultList();
+    }
+    
+    /**
+     * Finds events for a specific user
+     * 
+     * @param user the user to find events for
+     * @return list of calendar events for the user
+     */
+    public List<CalendarEvents> findByUser(Users user) {
+        return findByNamedQuery("CalendarEvents.findByUser", "user", user);
+    }
+    
 }