refactor: ICRUDService von IReadService erweitern und Methoden aktualisieren

- ICRUDService angepasst, um von IReadService zu erben, um die Wiederverwendbarkeit von Lesevorgängen zu fördern
- ICRUDService um `CreateAsync`- und `UpdateAsync`-Methoden mit geeigneten Rückgabetypen ergänzt
- Konsistenz gewährleistet durch Durchsetzung von IUnique<TId>-Einschränkungen für DTOs und Entitäten

DigitalData.Core.Abstractions/Application/IReadService.cs

@@ -0,0 +1,38 @@
+using DigitalData.Core.DTO;
+
+namespace DigitalData.Core.Abstractions.Application
+{
+    public interface IReadService<TReadDto, TEntity, TId>
+        where TReadDto : class where TEntity : class, IUnique<TId>
+    {
+        /// <summary>
+        /// Retrieves an entity by its identifier and returns its readDTO representation wrapped in an IServiceResult,
+        /// including the readDTO on success or null and an error message on failure.
+        /// </summary>
+        /// <param name="id">The identifier of the entity to retrieve.</param>
+        /// <returns>An DataResult containing the readDTO representing the found entity or null, with an appropriate message.</returns>
+        Task<DataResult<TReadDto>> ReadByIdAsync(TId id);
+
+        /// <summary>
+        /// Retrieves all entities and returns their readDTO representations wrapped in an IServiceResult,
+        /// including a collection of readDTOs on success or an error message on failure.
+        /// </summary>
+        /// <returns>An DataResult containing a collection of readDTOs representing all entities or an error message.</returns>
+        Task<DataResult<IEnumerable<TReadDto>>> ReadAllAsync();
+        
+        /// <summary>
+        /// Deletes an entity by its identifier and returns the result wrapped in an IServiceMessage,
+        /// indicating the success or failure of the operation, including the error messages on failure.
+        /// </summary>
+        /// <param name="id">The identifier of the entity to delete.</param>
+        /// <returns>An Result indicating the outcome of the delete operation, with an appropriate message.</returns>
+        Task<Result> DeleteAsyncById(TId id);
+
+        /// <summary>
+        /// Asynchronously checks if an entity with the specified identifier exists within the data store.
+        /// </summary>
+        /// <param name="id">The identifier of the entity to check.</param>
+        /// <returns>A task that represents the asynchronous operation. The task result contains a boolean value indicating whether the entity exists.</returns>
+        Task<bool> HasEntity(TId id);
+    }
+}