feat(rbac)!: add Azure RBAC engine, FFI API, and cross-language tests (#577)

- add Azure RBAC condition interpreter and builtin evaluation in core (expressions, parser updates, evaluator, and test harness)
- introduce comprehensive RBAC YAML test suites and coverage for i
  - action/suboperation
  - strings
  - numbers
  - bools
  - IP
  - GUID
  - dates
  - times
  - lists
  - quantifiers (ForAnyOfAnyValues, ForAllOfAllValues)
- expose RBAC evaluation through FFI with an `rbac` feature flag enabled by default
- add C# `RbacEngine` wrapper + P/Invoke entrypoint and document usage in C# README
- expand C# tests to execute all RBAC YAML cases with per-case logging
- wire test assets into C# test output and centralize YAML dependency versions

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

bindings/csharp/Regorus/NativeMethods.cs

@@ -492,6 +492,16 @@ namespace Regorus.Internal
 
         #endregion
 
+        #region RBAC Methods
+
+        /// <summary>
+        /// Evaluate an Azure RBAC condition expression against a JSON evaluation context.
+        /// </summary>
+        [DllImport(LibraryName, EntryPoint = "regorus_rbac_engine_eval_condition", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
+        internal static extern RegorusResult regorus_rbac_engine_eval_condition(byte* condition, byte* context_json);
+
+        #endregion
+
         #region Target Registry Methods
 
         /// <summary>

bindings/csharp/Regorus/RbacEngine.cs

@@ -0,0 +1,45 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System;
+using Regorus.Internal;
+
+#nullable enable
+namespace Regorus
+{
+    /// <summary>
+    /// Provides helpers for evaluating Azure RBAC condition expressions.
+    /// </summary>
+    public static unsafe class RbacEngine
+    {
+        /// <summary>
+        /// Evaluate an Azure RBAC condition expression against a JSON evaluation context.
+        /// </summary>
+        /// <param name="condition">Azure RBAC condition expression.</param>
+        /// <param name="contextJson">JSON encoded EvaluationContext.</param>
+        /// <returns>True if the condition evaluates to true; otherwise false.</returns>
+        /// <exception cref="Exception">Thrown when evaluation fails.</exception>
+        public static bool EvaluateCondition(string condition, string contextJson)
+        {
+            if (condition is null)
+            {
+                throw new ArgumentNullException(nameof(condition));
+            }
+
+            if (contextJson is null)
+            {
+                throw new ArgumentNullException(nameof(contextJson));
+            }
+
+            return Utf8Marshaller.WithUtf8(condition, conditionPtr =>
+                Utf8Marshaller.WithUtf8(contextJson, contextPtr =>
+                {
+                    unsafe
+                    {
+                        var result = Internal.API.regorus_rbac_engine_eval_condition((byte*)conditionPtr, (byte*)contextPtr);
+                        return ResultHelpers.GetBoolResult(result);
+                    }
+                }));
+        }
+    }
+}