Added SetUserPermissionsRequest model

Author: FrostyApeOne

src/GovUK.Dfe.CoreLibs.Contracts/ExternalApplications/Models/Request/SetUserPermissionsRequest.cs

@@ -0,0 +1,18 @@
+using System.Text.Json.Serialization;
+using GovUK.Dfe.CoreLibs.Contracts.ExternalApplications.Models.Response;
+
+namespace GovUK.Dfe.CoreLibs.Contracts.ExternalApplications.Models.Request;
+
+/// <summary>
+/// Request body for replacing a user's direct (user-level) permission grants.
+/// Does not affect permissions inherited from the user's role.
+/// </summary>
+public class SetUserPermissionsRequest
+{
+    /// <summary>
+    /// The complete set of user-level permission grants. Replaces all existing user-owned grants.
+    /// </summary>
+    [JsonPropertyName("permissions")]
+    public IReadOnlyCollection<RolePermissionGrantDto> Permissions { get; set; }
+        = Array.Empty<RolePermissionGrantDto>();
+}