Add net8.0-maccatalyst TFM to Microsoft.Identity.Client

Add Mac Catalyst target framework moniker (net8.0-maccatalyst) to the
main MSAL.NET library. Mac Catalyst uses UIKit like iOS, so the existing
iOS platform code (keychain, broker, webviews, HTTP client) is reused
directly without duplication.

Changes:
- Add TargetFrameworkNetMacCatalyst property and include in multi-target builds
- Define MACCATALYST and iOS compilation symbols for Mac Catalyst
- Add SupportedOSPlatformVersion 14.0 for Mac Catalyst
- Reuse Platforms/iOS source files for Mac Catalyst target
- Add JSON build infrastructure DefineConstants (same as iOS)
- Create PublicApi/net8.0-maccatalyst tracking files (copied from iOS)
- Differentiate product name telemetry (MSAL.MacCatalyst vs MSAL.Xamarin.iOS)
- Update CI mac build template with maccatalyst workload and build steps

This enables Mac Catalyst apps to get full platform-specific MSAL
functionality (keychain token caching, ASWebAuthenticationSession,
broker support, NSUrlSessionHandler) instead of falling back to
the generic netstandard2.0 build.

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

Author: mattleibow

build/platform_and_feature_flags.props

@@ -17,10 +17,13 @@
   <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetIos)'">
     <DefineConstants>$(DefineConstants);iOS;SUPPORTS_BROKER</DefineConstants>
   </PropertyGroup>
+  <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetMacCatalyst)'">
+    <DefineConstants>$(DefineConstants);MACCATALYST;iOS;SUPPORTS_BROKER</DefineConstants>
+  </PropertyGroup>
   <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetStandard)'">
     <DefineConstants>$(DefineConstants);NETSTANDARD;SUPPORTS_CONFIDENTIAL_CLIENT;SUPPORTS_BROKER;SUPPORTS_CUSTOM_CACHE;SUPPORTS_WIN32;</DefineConstants>
   </PropertyGroup>
-  <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetAndroid)' or '$(TargetFramework)' == '$(TargetFrameworkNetIos)'">
+  <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetAndroid)' or '$(TargetFramework)' == '$(TargetFrameworkNetIos)' or '$(TargetFramework)' == '$(TargetFrameworkNetMacCatalyst)'">
     <DefineConstants>$(DefineConstants);MOBILE</DefineConstants>
   </PropertyGroup>
 </Project>

src/client/Microsoft.Identity.Client/Microsoft.Identity.Client.csproj

@@ -12,17 +12,19 @@
   <PropertyGroup Condition="'$(INCLUDE_MOBILE_AND_LEGACY_TFM)' != ''">
     <TargetFrameworkNetAndroid>net8.0-android</TargetFrameworkNetAndroid>
     <TargetFrameworkNetIos>net8.0-ios</TargetFrameworkNetIos>
+    <TargetFrameworkNetMacCatalyst>net8.0-maccatalyst</TargetFrameworkNetMacCatalyst>
   </PropertyGroup>
 
   <!-- mobile SDK constraints -->
-  <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetIos)' or '$(TargetFramework)' == '$(TargetFrameworkNetAndroid)'">
+  <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetIos)' or '$(TargetFramework)' == '$(TargetFrameworkNetAndroid)' or '$(TargetFramework)' == '$(TargetFrameworkNetMacCatalyst)'">
     <SupportedOSPlatformVersion Condition="'$(TargetFramework)' == '$(TargetFrameworkNetIos)'">14.2</SupportedOSPlatformVersion>
     <SupportedOSPlatformVersion Condition="'$(TargetFramework)' == '$(TargetFrameworkNetAndroid)'">21.0</SupportedOSPlatformVersion>
+    <SupportedOSPlatformVersion Condition="'$(TargetFramework)' == '$(TargetFrameworkNetMacCatalyst)'">14.0</SupportedOSPlatformVersion>
   </PropertyGroup>
 
   <PropertyGroup>
-    <TargetFrameworks Condition="$([MSBuild]::IsOsPlatform('Windows'))">$(TargetFrameworkNetDesktop462);$(TargetFrameworkNetDesktop472);$(TargetFrameworkNetStandard);$(TargetFrameworkNetIos);$(TargetFrameworkNetAndroid);$(TargetFrameworkNet);</TargetFrameworks>
-    <TargetFrameworks Condition="$([MSBuild]::IsOsPlatform('OSX'))">$(TargetFrameworkNetStandard);$(TargetFrameworkNetIos);$(TargetFrameworkNetAndroid);$(TargetFrameworkNet)</TargetFrameworks>
+    <TargetFrameworks Condition="$([MSBuild]::IsOsPlatform('Windows'))">$(TargetFrameworkNetDesktop462);$(TargetFrameworkNetDesktop472);$(TargetFrameworkNetStandard);$(TargetFrameworkNetIos);$(TargetFrameworkNetMacCatalyst);$(TargetFrameworkNetAndroid);$(TargetFrameworkNet);</TargetFrameworks>
+    <TargetFrameworks Condition="$([MSBuild]::IsOsPlatform('OSX'))">$(TargetFrameworkNetStandard);$(TargetFrameworkNetIos);$(TargetFrameworkNetMacCatalyst);$(TargetFrameworkNetAndroid);$(TargetFrameworkNet)</TargetFrameworks>
     <TargetFrameworks Condition="$([MSBuild]::IsOsPlatform('Linux')) Or '$(NetCoreOnly)' !='' ">$(TargetFrameworkNetStandard);$(TargetFrameworkNet)</TargetFrameworks>
   </PropertyGroup>
 
@@ -60,7 +62,7 @@
     <DefineConstants>$(DefineConstants);HAVE_ADO_NET;HAVE_APP_DOMAIN;HAVE_ASYNC;HAVE_BIG_INTEGER;HAVE_BINARY_FORMATTER;HAVE_BINARY_SERIALIZATION;HAVE_BINARY_EXCEPTION_SERIALIZATION;HAVE_CHAR_TO_LOWER_WITH_CULTURE;HAVE_CHAR_TO_STRING_WITH_CULTURE;HAVE_COM_ATTRIBUTES;HAVE_COMPONENT_MODEL;HAVE_CONCURRENT_COLLECTIONS;HAVE_COVARIANT_GENERICS;HAVE_DATA_CONTRACTS;HAVE_DATE_TIME_OFFSET;HAVE_DB_NULL_TYPE_CODE;HAVE_DYNAMIC;HAVE_EMPTY_TYPES;HAVE_ENTITY_FRAMEWORK;HAVE_EXPRESSIONS;HAVE_FAST_REVERSE;HAVE_FSHARP_TYPES;HAVE_FULL_REFLECTION;HAVE_GUID_TRY_PARSE;HAVE_HASH_SET;HAVE_ICLONEABLE;HAVE_ICONVERTIBLE;HAVE_IGNORE_DATA_MEMBER_ATTRIBUTE;HAVE_INOTIFY_COLLECTION_CHANGED;HAVE_INOTIFY_PROPERTY_CHANGING;HAVE_ISET;HAVE_LINQ;HAVE_MEMORY_BARRIER;HAVE_METHOD_IMPL_ATTRIBUTE;HAVE_NON_SERIALIZED_ATTRIBUTE;HAVE_READ_ONLY_COLLECTIONS;HAVE_REFLECTION_EMIT;HAVE_SECURITY_SAFE_CRITICAL_ATTRIBUTE;HAVE_SERIALIZATION_BINDER_BIND_TO_NAME;HAVE_STREAM_READER_WRITER_CLOSE;HAVE_STRING_JOIN_WITH_ENUMERABLE;HAVE_TIME_SPAN_PARSE_WITH_CULTURE;HAVE_TIME_SPAN_TO_STRING_WITH_CULTURE;HAVE_TIME_ZONE_INFO;HAVE_TRACE_WRITER;HAVE_TYPE_DESCRIPTOR;HAVE_UNICODE_SURROGATE_DETECTION;HAVE_VARIANT_TYPE_PARAMETERS;HAVE_VERSION_TRY_PARSE;HAVE_XLINQ;HAVE_XML_DOCUMENT;HAVE_XML_DOCUMENT_TYPE;HAVE_CONCURRENT_DICTIONARY;$(AdditionalConstants)</DefineConstants>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
-  <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetIos)'">
+  <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetIos)' or '$(TargetFramework)' == '$(TargetFrameworkNetMacCatalyst)'">
     <!-- These are for MSAL json/* build infra -->
     <DefineConstants>$(DefineConstants);HAVE_ASYNC;HAVE_BINARY_SERIALIZATION;HAVE_COVARIANT_GENERICS;HAVE_DATA_CONTRACTS;HAVE_DATE_TIME_OFFSET;HAVE_DYNAMIC;HAVE_EXPRESSIONS;HAVE_FSHARP_TYPES;HAVE_GUID_TRY_PARSE;HAVE_HASH_SET;HAVE_IGNORE_DATA_MEMBER_ATTRIBUTE;HAVE_INOTIFY_COLLECTION_CHANGED;HAVE_INOTIFY_PROPERTY_CHANGING;HAVE_ISET;HAVE_LINQ;HAVE_METHOD_IMPL_ATTRIBUTE;HAVE_NON_SERIALIZED_ATTRIBUTE;HAVE_READ_ONLY_COLLECTIONS;HAVE_REFLECTION_BINDER;HAVE_SERIALIZATION_BINDER_BIND_TO_NAME;HAVE_STRING_JOIN_WITH_ENUMERABLE;HAVE_TIME_SPAN_PARSE_WITH_CULTURE;HAVE_TIME_SPAN_TO_STRING_WITH_CULTURE;HAVE_TIME_ZONE_INFO;HAVE_UNICODE_SURROGATE_DETECTION;HAVE_VARIANT_TYPE_PARAMETERS;HAVE_VERSION_TRY_PARSE;HAVE_XLINQ;HAVE_XML_DOCUMENT;HAVE_CONCURRENT_DICTIONARY;HAVE_ICONVERTIBLE;HAVE_XML_DOCUMENT_TYPE;$(AdditionalConstants)</DefineConstants>
   </PropertyGroup>
@@ -146,7 +148,7 @@
     <PackageReference Update="System.Security.SecureString" />
     <PackageReference Include="Xamarin.AndroidX.Browser" PrivateAssets="All" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetIos)'">
+  <ItemGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetIos)' or '$(TargetFramework)' == '$(TargetFrameworkNetMacCatalyst)'">
     <Compile Include="$(PathToMsalSources)\Platforms\iOS\**\*.cs" />
     <Compile Include="$(PathToMsalSources)\PlatformsCommon\PlatformNotSupported\ApiConfig\SystemWebViewOptions.cs" />
     <PackageReference Update="System.Security.SecureString" />

src/client/Microsoft.Identity.Client/Platforms/iOS/iOSPlatformProxy.cs

@@ -54,7 +54,11 @@ public override string GetDefaultRedirectUri(string clientId, bool useRecommende
 
         protected override  string InternalGetProductName()
         {
+#if MACCATALYST
+            return "MSAL.MacCatalyst";
+#else
             return "MSAL.Xamarin.iOS";
+#endif
         }
 
         /// <summary>