Add XML documentation across gateway, worker, and .NET client

src/MxGateway.Server/Configuration/GatewayOptionsValidator.cs

@@ -8,6 +8,12 @@ public sealed class GatewayOptionsValidator : IValidateOptions<GatewayOptions>
     private const int MinimumMaxMessageBytes = 1024;
     private const int MaximumMaxMessageBytes = 256 * 1024 * 1024;
 
+    /// <summary>
+    /// Validates gateway configuration options.
+    /// </summary>
+    /// <param name="name">Options name.</param>
+    /// <param name="options">Gateway options to validate.</param>
+    /// <returns>Validation result.</returns>
     public ValidateOptionsResult Validate(string? name, GatewayOptions options)
     {
         List<string> failures = [];