Added extendability to the sign-in / sync, the session validation and the frontend claims transfer calls

Moonlight.ApiServer/Interfaces/IAuthCheckExtension.cs

@@ -0,0 +1,16 @@
+using System.Security.Claims;
+using Moonlight.Shared.Http.Responses.Auth;
+
+namespace Moonlight.ApiServer.Interfaces;
+
+public interface IAuthCheckExtension
+{
+    /// <summary>
+    /// This function will be called by the frontend reaching out to the api server for claim information.
+    /// You can use this function to give your frontend plugins access to user specific data which is
+    /// static for the session. E.g. the avatar url of a user
+    /// </summary>
+    /// <param name="principal">The principal of the current signed-in user</param>
+    /// <returns>An array of claim responses which gets added to the list of claims to send to the frontend</returns>
+    public Task<AuthClaimResponse[]> GetFrontendClaims(ClaimsPrincipal principal);
+}