feat: ReadAll-Methode in ICRUDRepository und CRUDRepository implementieren

- ReadAll-Methode zur ICRUDRepository-Schnittstelle hinzugefügt, um die Abfrage aller Entitäten zu ermöglichen.
- ReadAll-Methode in der CRUDRepository-Klasse implementiert, um IQueryable<TEntity> für weitere Abfragen und Filterung bereitzustellen.

DigitalData.Core.Abstractions/Infrastructure/ICRUDRepository.cs

@@ -21,6 +21,16 @@
         /// <returns>The entity found, or null if no entity is found.</returns>
         Task<TEntity?> ReadByIdAsync(TId id);
 
+        /// <summary>
+        /// Retrieves all entities of type <typeparamref name="TEntity"/> from the repository.
+        /// </summary>
+        /// <remarks>
+        /// This method returns an <see cref="IQueryable{TEntity}"/> that represents all entities in the repository. 
+        /// The result is an IQueryable that allows for further querying and filtering to be applied by the caller.
+        /// </remarks>
+        /// <returns>An <see cref="IQueryable{TEntity}"/> containing all entities of type <typeparamref name="TEntity"/> in the repository.</returns>
+        protected IQueryable<TEntity> ReadAll();
+
         /// <summary>
         /// Retrieves all entities from the repository.
         /// </summary>