Added oauth2 access endpoint override option

Moonlight.ApiServer/Configuration/AppConfiguration.cs

@@ -41,6 +41,7 @@ public class AppConfiguration
             public string ClientId { get; set; } = Formatter.GenerateString(8);
             public string ClientSecret { get; set; } = Formatter.GenerateString(32);
             public string? AuthorizationEndpoint { get; set; }
+            public string? AccessEndpoint { get; set; }
             public string? AuthorizationRedirect { get; set; }
         }
     }

Moonlight.ApiServer/Http/Controllers/Auth/AuthController.cs

@@ -68,8 +68,15 @@ public class AuthController : Controller
 
         // Create http client to call the auth provider
         using var httpClient = new HttpClient();
-        httpClient.BaseAddress = new Uri(Configuration.PublicUrl);
-        httpClient.DefaultRequestHeaders.Add("Authorization", $"Basic {Configuration.Authentication.OAuth2.ClientSecret}");
+        
+        httpClient.BaseAddress = new Uri(
+            string.IsNullOrEmpty(Configuration.Authentication.OAuth2.AccessEndpoint)
+                ? Configuration.PublicUrl
+                : Configuration.Authentication.OAuth2.AccessEndpoint
+        );
+        
+        httpClient.DefaultRequestHeaders.Add("Authorization",
+            $"Basic {Configuration.Authentication.OAuth2.ClientSecret}");
 
         var httpApiClient = new HttpApiClient(httpClient);