Improve error logging

Author: Jakubk15

src/main/java/com/eternalcode/parcellockers/database/DatabaseManager.java

@@ -91,7 +91,7 @@ public void disconnect() {
             this.dataSource.close();
             this.connectionSource.close();
         } catch (Exception exception) {
-            exception.printStackTrace();
+            this.logger.severe("Failed to disconnect from the database: " + exception.getMessage());
         }
     }