fix: resolve CS0281 InternalsVisibleTo signing mismatch in Authentication tests

Replace #if DEBUG conditional in InternalsVisibleTo attributes with
signing-aware logic that works for both signed and unsigned Release builds.

- Authentication/AssemblyInfo.cs: use unconditional simple form since this
  assembly is never delay-signed at compile time
- Authentication.Core/AssemblyInfo.cs: use #if SIGNED_BUILD conditional
  tied to actual SignAssembly MSBuild property
- Authentication.Core.csproj: define SIGNED_BUILD constant when
  SignAssembly=true

Fixes #3561

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: gavinbarron

src/Authentication/Authentication.Core/Microsoft.Graph.Authentication.Core.csproj

@@ -12,6 +12,9 @@
     <EnableNETAnalyzers>true</EnableNETAnalyzers>
     <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
   </PropertyGroup>
+  <PropertyGroup Condition="'$(SignAssembly)' == 'true'">
+    <DefineConstants>$(DefineConstants);SIGNED_BUILD</DefineConstants>
+  </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Azure.Identity" Version="1.18.0" />
     <PackageReference Include="Azure.Identity.Broker" Version="1.4.0" />

src/Authentication/Authentication.Core/Properties/AssemblyInfo.cs

@@ -1,7 +1,7 @@
 using System.Runtime.CompilerServices;
 
-#if DEBUG
-[assembly: InternalsVisibleTo("Microsoft.Graph.Authentication.Test")]
-#else
+#if SIGNED_BUILD
 [assembly: InternalsVisibleTo("Microsoft.Graph.Authentication.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9")]
+#else
+[assembly: InternalsVisibleTo("Microsoft.Graph.Authentication.Test")]
 #endif

src/Authentication/Authentication/Properties/AssemblyInfo.cs

@@ -1,7 +1,3 @@
 using System.Runtime.CompilerServices;
 
-#if DEBUG
 [assembly: InternalsVisibleTo("Microsoft.Graph.Authentication.Test")]
-#else
-[assembly: InternalsVisibleTo("Microsoft.Graph.Authentication.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9")]
-#endif