Deprecate controllers/services; simplify generics

Added `[Obsolete("Use MediatR")]` attributes to various controller and service classes to indicate deprecation in favor of MediatR. Simplified generic type constraints in `CRUDControllerBase` and related files by removing `IUnique<TId>`. Improved structure and documentation in `CSPMiddleware.cs`. Introduced new extension methods in `EntityExtensions.cs` for safer retrieval of 'Id' properties. Removed `IUnique.cs` interface and updated project dependencies in `DigitalData.Core.Application.csproj` for caching. Overall, these changes enhance code maintainability and clarity.

DigitalData.Core.API/CSPMiddleware.cs

@@ -1,47 +1,46 @@
-namespace DigitalData.Core.API
+namespace DigitalData.Core.API;
+
+/// <summary>
+/// Middleware to add Content Security Policy (CSP) headers to the HTTP response.
+/// </summary>
+public class CSPMiddleware
 {
+    private readonly RequestDelegate _next;
+    private readonly string _policy;
+
     /// <summary>
-    /// Middleware to add Content Security Policy (CSP) headers to the HTTP response.
+    /// Initializes a new instance of the <see cref="CSPMiddleware"/> class.
     /// </summary>
-    public class CSPMiddleware
+    /// <param name="next">The next middleware in the request pipeline.</param>
+    /// <param name="policy">The CSP policy string with placeholders for nonces.</param>
+    public CSPMiddleware(RequestDelegate next, string policy)
     {
-        private readonly RequestDelegate _next;
-        private readonly string _policy;
+        _next = next;
+        _policy = policy;
+    }
 
-        /// <summary>
-        /// Initializes a new instance of the <see cref="CSPMiddleware"/> class.
-        /// </summary>
-        /// <param name="next">The next middleware in the request pipeline.</param>
-        /// <param name="policy">The CSP policy string with placeholders for nonces.</param>
-        public CSPMiddleware(RequestDelegate next, string policy)
+    /// <summary>
+    /// Invokes the middleware to add the CSP header to the response.
+    /// </summary>
+    /// <param name="context">The HTTP context.</param>
+    /// <returns>A task that represents the completion of request processing.</returns>
+    public async Task Invoke(HttpContext context)
+    {
+        // Generate a nonce (number used once) for inline scripts and styles
+        var nonce = Convert.ToBase64String(Guid.NewGuid().ToByteArray());
+
+        // Store the nonce in the context items for later use
+        context.Items["csp-nonce"] = nonce;
+
+        // Add the CSP header to the response
+        context.Response.OnStarting(() =>
         {
-            _next = next;
-            _policy = policy;
-        }
+            context.Response.Headers.Append("Content-Security-Policy",
+                string.Format(_policy, nonce));
+            return Task.CompletedTask;
+        });
 
-        /// <summary>
-        /// Invokes the middleware to add the CSP header to the response.
-        /// </summary>
-        /// <param name="context">The HTTP context.</param>
-        /// <returns>A task that represents the completion of request processing.</returns>
-        public async Task Invoke(HttpContext context)
-        {
-            // Generate a nonce (number used once) for inline scripts and styles
-            var nonce = Convert.ToBase64String(Guid.NewGuid().ToByteArray());
-
-            // Store the nonce in the context items for later use
-            context.Items["csp-nonce"] = nonce;
-
-            // Add the CSP header to the response
-            context.Response.OnStarting(() =>
-            {
-                context.Response.Headers.Add("Content-Security-Policy",
-                    string.Format(_policy, nonce));
-                return Task.CompletedTask;
-            });
-
-            // Call the next middleware in the pipeline
-            await _next(context);
-        }
+        // Call the next middleware in the pipeline
+        await _next(context);
     }
 }