feature(#6): this commit defines the contract for the permission namespace policy service

Author: https-richardy

Source/HttpsRichardy.Federation.Domain/Policies/IPermissionNamespacePolicy.cs

@@ -0,0 +1,20 @@
+namespace HttpsRichardy.Federation.Domain.Policies;
+
+// defines a policy responsible for protecting the system permission namespace
+// from unauthorized usage by realms
+
+// certain permissions are reserved by the federation system and represent
+// privileged administrative capabilities (e.g. managing realms or federation resources)
+
+// this policy ensures that realms cannot create or manipulate permissions
+// whose identifiers belong to the reserved system namespace, preventing
+// privilege escalation through permission name collision
+
+public interface IPermissionNamespacePolicy
+{
+    public Task<Result> EnsurePermissionIsAllowedAsync(
+        Realm realm,
+        Permission permission,
+        CancellationToken cancellation = default
+    );
+}