Declare AddScheme's displayName parameter as nullable (#25480)

Author: kevinchalet

src/Http/Authentication.Abstractions/src/AuthenticationOptions.cs

@@ -55,7 +55,7 @@ public void AddScheme(string name, Action<AuthenticationSchemeBuilder> configure
         /// <typeparam name="THandler">The <see cref="IAuthenticationHandler"/> responsible for the scheme.</typeparam>
         /// <param name="name">The name of the scheme being added.</param>
         /// <param name="displayName">The display name for the scheme.</param>
-        public void AddScheme<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)]THandler>(string name, string displayName) where THandler : IAuthenticationHandler
+        public void AddScheme<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)]THandler>(string name, string? displayName) where THandler : IAuthenticationHandler
             => AddScheme(name, b =>
             {
                 b.DisplayName = displayName;