Refactor and enhance static ReCClient configuration

Introduced a new `BuildStaticClient(Action<StaticBuildConfiguration>)` method for flexible and detailed static `IServiceProvider` configuration. Added the `StaticBuildConfiguration` class to encapsulate optional settings like `BaseAddress`, `ConfigureClient`, `Logger`, and more.

Refactored existing `BuildStaticClient` overloads to use the new method, ensuring consistency and reducing duplication. Added support for optional `ILogger` instances and improved validation to enforce proper configuration.

Marked existing `BuildStaticClient` methods as obsolete, recommending the new method. Enhanced thread-safety using `Interlocked.CompareExchange`. Updated XML documentation and added conditional compilation for `NETFRAMEWORK` compatibility.

These changes improve maintainability, usability, and alignment with modern .NET practices.

src/ReC.Client/ReCClient.cs

@@ -101,6 +101,53 @@ namespace ReC.Client
             return services.BuildServiceProvider();
         }, System.Threading.LazyThreadSafetyMode.ExecutionAndPublication);
 
+        /// <summary>
+        /// Configures and builds the static <see cref="IServiceProvider"/> for creating <see cref="ReCClient"/> instances.
+        /// </summary>
+        /// <remarks>
+        /// This method should only be called once during application startup. The underlying
+        /// <see cref="IServiceProvider"/> is created lazily and thread-safely on first access via <see cref="Create"/>.
+        /// </remarks>
+        /// <param name="configure">Callback that populates a <see cref="StaticBuildConfiguration"/> instance.</param>
+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="configure"/> is null.</exception>
+        /// <exception cref="InvalidOperationException">Thrown when neither <see cref="StaticBuildConfiguration.BaseAddress"/> nor <see cref="StaticBuildConfiguration.ConfigureClient"/> is set, when both are set, or when the static provider has already been built.</exception>
+        [Obsolete("Use a local service collection instead of the static provider.")]
+        public static void BuildStaticClient(Action<StaticBuildConfiguration> configure)
+        {
+            if (configure == null)
+                throw new ArgumentNullException(nameof(configure));
+
+            var cfg = new StaticBuildConfiguration();
+            configure(cfg);
+
+            var hasBaseAddress = !string.IsNullOrWhiteSpace(cfg.BaseAddress);
+            var hasConfigureClient = cfg.ConfigureClient != null;
+
+            if (!hasBaseAddress && !hasConfigureClient)
+                throw new InvalidOperationException(
+                    $"Either {nameof(StaticBuildConfiguration.BaseAddress)} or {nameof(StaticBuildConfiguration.ConfigureClient)} must be set on {nameof(StaticBuildConfiguration)}.");
+
+            if (hasBaseAddress && hasConfigureClient)
+                throw new InvalidOperationException(
+                    $"{nameof(StaticBuildConfiguration.BaseAddress)} and {nameof(StaticBuildConfiguration.ConfigureClient)} are mutually exclusive on {nameof(StaticBuildConfiguration)}.");
+
+            Action<IServiceCollection> register = services =>
+            {
+                if (hasBaseAddress)
+                    services.AddRecClient(cfg.BaseAddress, cfg.ConfigureOptions);
+                else
+                    services.AddRecClient(cfg.ConfigureClient, cfg.ConfigureOptions);
+
+                if (cfg.Logger != null)
+                    services.AddSingleton(cfg.Logger);
+
+                cfg.ConfigureServices?.Invoke(services);
+            };
+
+            if (System.Threading.Interlocked.CompareExchange(ref _staticConfigure, register, null) != null)
+                throw new InvalidOperationException("Static Provider is already built.");
+        }
+
         /// <summary>
         /// Configures and builds the static <see cref="IServiceProvider"/> for creating <see cref="ReCClient"/> instances.
         /// </summary>
@@ -110,17 +157,21 @@ namespace ReC.Client
         /// </remarks>
         /// <param name="apiUri">The base URI of the ReC API.</param>
         /// <param name="configureOptions">An optional callback to configure <see cref="ReCClientOptions"/>.</param>
+        /// <param name="logger">An optional <see cref="ILogger"/> instance to be used by the <see cref="ReCClient"/>. When provided, it is registered as a singleton in the internal service collection.</param>
         /// <exception cref="InvalidOperationException">Thrown if the static provider has already been built.</exception>
-        [Obsolete("Use a local service collection instead of the static provider.")]
+        [Obsolete("Use BuildStaticClient(Action<StaticBuildConfiguration>) instead.")]
 #if NETFRAMEWORK
-        public static void BuildStaticClient(string apiUri, Action<ReCClientOptions> configureOptions = null)
+        public static void BuildStaticClient(string apiUri, Action<ReCClientOptions> configureOptions = null, ILogger logger = null)
 #else
-        public static void BuildStaticClient(string apiUri, Action<ReCClientOptions>? configureOptions = null)
+        public static void BuildStaticClient(string apiUri, Action<ReCClientOptions>? configureOptions = null, ILogger<ReCClient>? logger = null)
 #endif
         {
-            Action<IServiceCollection> configure = services => services.AddRecClient(apiUri, configureOptions);
+            BuildStaticClient(cfg =>
-            if (System.Threading.Interlocked.CompareExchange(ref _staticConfigure, configure, null) != null)
+            {
-                throw new InvalidOperationException("Static Provider is already built.");
+                cfg.BaseAddress = apiUri;
+                cfg.ConfigureOptions = configureOptions;
+                cfg.Logger = logger;
+            });
         }
 
         /// <summary>
@@ -132,17 +183,21 @@ namespace ReC.Client
         /// </remarks>
         /// <param name="configureClient">An action to configure the <see cref="HttpClient"/>.</param>
         /// <param name="configureOptions">An optional callback to configure <see cref="ReCClientOptions"/>.</param>
+        /// <param name="logger">An optional <see cref="ILogger"/> instance to be used by the <see cref="ReCClient"/>. When provided, it is registered as a singleton in the internal service collection.</param>
         /// <exception cref="InvalidOperationException">Thrown if the static provider has already been built.</exception>
-        [Obsolete("Use a local service collection instead of the static provider.")]
+        [Obsolete("Use BuildStaticClient(Action<StaticBuildConfiguration>) instead.")]
 #if NETFRAMEWORK
-        public static void BuildStaticClient(Action<HttpClient> configureClient, Action<ReCClientOptions> configureOptions = null)
+        public static void BuildStaticClient(Action<HttpClient> configureClient, Action<ReCClientOptions> configureOptions = null, ILogger logger = null)
 #else
-        public static void BuildStaticClient(Action<HttpClient> configureClient, Action<ReCClientOptions>? configureOptions = null)
+        public static void BuildStaticClient(Action<HttpClient> configureClient, Action<ReCClientOptions>? configureOptions = null, ILogger<ReCClient>? logger = null)
 #endif
         {
-            Action<IServiceCollection> configure = services => services.AddRecClient(configureClient, configureOptions);
+            BuildStaticClient(cfg =>
-            if (System.Threading.Interlocked.CompareExchange(ref _staticConfigure, configure, null) != null)
+            {
-                throw new InvalidOperationException("Static Provider is already built.");
+                cfg.ConfigureClient = configureClient;
+                cfg.ConfigureOptions = configureOptions;
+                cfg.Logger = logger;
+            });
         }
 
         /// <summary>

src/ReC.Client/StaticBuildConfiguration.cs

@@ -0,0 +1,63 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using System;
+using System.Net.Http;
+
+namespace ReC.Client
+{
+    /// <summary>
+    /// Configuration object for <see cref="ReCClient.BuildStaticClient(Action{StaticBuildConfiguration})"/>.
+    /// Groups all optional settings for the static <see cref="ReCClient"/> bootstrap path.
+    /// </summary>
+    /// <remarks>
+    /// Either <see cref="BaseAddress"/> or <see cref="ConfigureClient"/> must be set; setting both at the same time is not allowed.
+    /// </remarks>
+    public class StaticBuildConfiguration
+    {
+        /// <summary>
+        /// Base URI of the ReC API. Mutually exclusive with <see cref="ConfigureClient"/>.
+        /// </summary>
+#if NETFRAMEWORK
+        public string BaseAddress { get; set; }
+#else
+        public string? BaseAddress { get; set; }
+#endif
+
+        /// <summary>
+        /// Callback that configures the underlying <see cref="HttpClient"/>. Mutually exclusive with <see cref="BaseAddress"/>.
+        /// </summary>
+#if NETFRAMEWORK
+        public Action<HttpClient> ConfigureClient { get; set; }
+#else
+        public Action<HttpClient>? ConfigureClient { get; set; }
+#endif
+
+        /// <summary>
+        /// Optional callback to configure <see cref="ReCClientOptions"/>.
+        /// </summary>
+#if NETFRAMEWORK
+        public Action<ReCClientOptions> ConfigureOptions { get; set; }
+#else
+        public Action<ReCClientOptions>? ConfigureOptions { get; set; }
+#endif
+
+        /// <summary>
+        /// Optional logger instance to be registered as a singleton in the internal service collection.
+        /// </summary>
+#if NETFRAMEWORK
+        public ILogger Logger { get; set; }
+#else
+        public ILogger<ReCClient>? Logger { get; set; }
+#endif
+
+        /// <summary>
+        /// Optional callback for additional service registrations on the internal <see cref="IServiceCollection"/>
+        /// (e.g. <c>services.AddLogging(...)</c> or custom dependencies).
+        /// </summary>
+#if NETFRAMEWORK
+        public Action<IServiceCollection> ConfigureServices { get; set; }
+#else
+        public Action<IServiceCollection>? ConfigureServices { get; set; }
+#endif
+    }
+}