Refactor namespaces and enhance application structure

This commit reorganizes namespaces from `DigitalData.Core.Abstractions` and `DigitalData.Core.DTO` to `DigitalData.Core.Application.Interfaces` and `DigitalData.Core.Application.DTO`, improving maintainability and clarity.

Updated using directives across multiple files to reflect the new structure, ensuring functionality remains intact.

Project references in `DigitalData.Core.API.csproj` have been consolidated to include the new Application project.

Introduced new classes and interfaces such as `BaseDTO`, `CookieConsentSettings`, `DataResult`, `Notice`, and `Result` to enhance data transfer and service result handling.

Updated `IRepository`, `ICRUDRepository`, and `IEntityMapper` interfaces to facilitate CRUD operations and entity mapping.

Added extension methods in `Extensions.cs` to improve repository usability.

New interfaces for HTTP client services have been added, enhancing external API call handling.

Overall, these changes reflect a significant restructuring aimed at improving organization and preparing for future development.

DigitalData.Core.Application/DTO/DataResult.cs

@@ -0,0 +1,26 @@
+using System.Text.Json.Serialization;
+
+namespace DigitalData.Core.Application.DTO
+{
+    /// <summary>
+    /// Represents a result of an operation that includes data, inheriting from <see cref="Result"/>.
+    /// </summary>
+    /// <typeparam name="T">The type of the data included in the result.</typeparam>
+    public class DataResult<T> : Result
+    {
+        /// <summary>
+        /// Gets or sets the data included in the result. This property is required.
+        /// It will be ignored during JSON serialization if the value is null.
+        /// </summary>
+        [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+        public required T Data { get; set; }
+
+        /// <summary>
+        /// Converts the current <see cref="DataResult{T}"/> to a failed <see cref="DataResult{I}"/>,
+        /// preserving the messages and notices.
+        /// </summary>
+        /// <typeparam name="I">The type of the data in the new failed result.</typeparam>
+        /// <returns>A failed <see cref="DataResult{I}"/> with the current messages and notices.</returns>
+        public DataResult<I> ToFail<I>() => Fail<I>().Message(Messages).Notice(Notices);
+    }
+}