What does the message "symfony Cannot find the entity manager for class 'App\Entity\User'" mean?

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This message means that Symfony is unable to find the entity manager for the specified class 'App\Entity\User'. An entity manager is responsible for managing the persistence and retrieval of entities in a database, and this error occurs when Symfony is unable to locate the correct entity manager for the User class. This may happen if the entity manager is not properly configured or if there is a typo or error in the class name or namespace.