Enhance ReC.Client library with new features and cleanup

- Added comprehensive XML documentation for `DependencyInjection`
  and `ReCClient` classes to improve code readability.
- Introduced overload for `AddRecClient` to allow flexible
  `HttpClient` configuration.
- Added static `BuildStaticClient` and `Create` methods for
  simplified client instantiation.
- Marked synchronous `InvokeRecAction` method as obsolete to
  encourage asynchronous usage.
- Updated `ReC.Client.csproj`:
  - Added `<DocumentationFile>` property for XML doc generation.
  - Downgraded `Microsoft.Extensions.Http` to version 8.0.0.
  - Removed `System.Text.Json` package reference.
- Removed `System.Text.Json` dependency from `ReCClient.cs`.
- Generated unique `HttpClient` name for `ReCClient` instances.
- Performed general code cleanup and improved method remarks.

src/ReC.Client/DependencyInjection.cs

@@ -6,8 +6,17 @@ using System.Net.Http;
 
 namespace ReC.Client
 {
+    /// <summary>
+    /// Provides extension methods for setting up the ReC client in an <see cref="IServiceCollection"/>.
+    /// </summary>
     public static class DependencyInjection
     {
+        /// <summary>
+        /// Adds and configures the <see cref="HttpClient"/> for the <see cref="ReCClient"/> to the specified <see cref="IServiceCollection"/>
+        /// </summary>
+        /// <param name="services">The <see cref="IServiceCollection"/> to add the services to.</param>
+        /// <param name="apiUri">The base URI of the ReC API.</param>
+        /// <returns>An <see cref="IHttpClientBuilder"/> that can be used to configure the client.</returns>
         public static IHttpClientBuilder AddRecClient(this IServiceCollection services, string apiUri)
         {
             return services.AddHttpClient(ReCClient.ClientName, client =>
@@ -16,6 +25,12 @@ namespace ReC.Client
             });
         }
 
+        /// <summary>
+        /// Adds and configures the <see cref="HttpClient"/> for the <see cref="ReCClient"/> to the specified <see cref="IServiceCollection"/>
+        /// </summary>
+        /// <param name="services">The <see cref="IServiceCollection"/> to add the services to.</param>
+        /// <param name="configureClient">An action to configure the <see cref="HttpClient"/>.</param>
+        /// <returns>An <see cref="IHttpClientBuilder"/> that can be used to configure the client.</returns>
         public static IHttpClientBuilder AddRecClient(this IServiceCollection services, Action<HttpClient> configureClient)
         {
             return services.AddHttpClient(ReCClient.ClientName, configureClient);