Managed Identity and Service Principal Support (#492)

# Overview
- Added MSAL Managed Identity and Service Principal Token Providers to
Microsoft.Artifacts.Authentication Library.
- Created new endpoint `ARTIFACTS_CREDENTIALPROVIDER_FEED_ENDPOINTS`
environment variable with new json schema for MI/SP required fields.
- Updated VstsBuildTaskServiceEndpointCredentialProvider to call
Microsoft.Artifacts.Authentication for MI/SP token providers.
- Reverted #485 Changes to use system.text.json for de/serialization
everywhere except for the `VSS_NUGET_EXTERNAL_FEED_ENDPOINTS`
environment variable.

## Design Decisions
- Intentionally not supporting SP secrets authentication to promote
security best practices.
- The new environment variable name and json schema were created instead
of reusing or extending the existing `VSS_NUGET_EXTERNAL_FEED_ENDPOINTS`
to reduce password usage and clarify the environment variable will be
available to our other credproviders such as the
[artifacs-keyring](https://github.com/microsoft/artifacts-keyring) not
just NuGet.

## Environment Variable
 `ARTIFACTS_CREDENTIALPROVIDER_FEED_ENDPOINTS` 
```javascript
 {"endpointCredentials": [{"endpoint":"http://example.index.json", "clientId":"required", "clientCertificateSubjectName":"optional", "clientCertificateFilePath":"optional"}]}
```
- `endpoint`: required. Feed url to authenticate against. 
- `clientId`: required for both MI/SP. For user assigned managed
identities enter the Entra client id. For system assigned variables set
the value to `system`.
- `clientCertificateSubjectName`: Subject Name of the certificate
located in the My/ CurrentUser or LocalMachine certificate store.
Optional field. Only used by SP authentication.
- `clientCertificateFilePath`: File path location of the certificate on
the machine. Optional field. Only used by SP authentication.

Will throw error if both `clientCertificateSubjectName` or
`clientCertificateFilePath` are specified.

CredentialProvider.Microsoft.Tests/CredentialProvider.Microsoft.Tests.csproj

@@ -4,6 +4,8 @@
   <PropertyGroup>
     <LangVersion>latest</LangVersion>
     <IsPackable>false</IsPackable>
+    <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
+    <GenerateBindingRedirectsOutputType>true</GenerateBindingRedirectsOutputType>
   </PropertyGroup>
 
   <ItemGroup>
@@ -18,5 +20,4 @@
     <ProjectReference Include="..\CredentialProvider.Microsoft\CredentialProvider.Microsoft.csproj" />
     <ProjectReference Include="..\src\Authentication\Microsoft.Artifacts.Authentication.csproj" />
   </ItemGroup>
-
 </Project>

CredentialProvider.Microsoft.Tests/CredentialProviders/Vsts/AuthUtilTests.cs

@@ -45,27 +45,27 @@ public void TestCleanup()
         }
 
         [TestMethod]
-        public async Task GetAadAuthorityUri_WithoutAuthenticateHeaders_ReturnsCorrectAuthority()
+        public async Task GetAuthorizationInfoAsync_WithoutAuthenticateHeaders_ReturnsCorrectAuthority()
         {
             var requestUri = new Uri("https://example.pkgs.visualstudio.com/_packaging/feed/nuget/v3/index.json");
 
-            var authorityUri = await authUtil.GetAadAuthorityUriAsync(requestUri, cancellationToken);
+            var authInfo = await authUtil.GetAuthorizationInfoAsync(requestUri, cancellationToken);
 
-            authorityUri.Should().Be(organizationsAuthority);
+            authInfo.EntraAuthorityUri.Should().Be(organizationsAuthority);
         }
 
         [TestMethod]
-        public async Task GetAadAuthorityUri_WithoutAuthenticateHeadersAndPpe_ReturnsCorrectAuthority()
+        public async Task GetAuthorizationInfoAsync_WithoutAuthenticateHeadersAndPpe_ReturnsCorrectAuthority()
         {
             var requestUri = new Uri("https://example.pkgs.vsts.me/_packaging/feed/nuget/v3/index.json");
 
-            var authorityUri = await authUtil.GetAadAuthorityUriAsync(requestUri, cancellationToken);
+            var authInfo = await authUtil.GetAuthorizationInfoAsync(requestUri, cancellationToken);
 
-            authorityUri.Should().Be(new Uri("https://login.windows-ppe.net/organizations"));
+            authInfo.EntraAuthorityUri.Should().Be(new Uri("https://login.windows-ppe.net/organizations"));
         }
 
         [TestMethod]
-        public async Task GetAadAuthorityUri_WithoutAuthenticateHeadersAndPpeAndPpeOverride_ReturnsCorrectAuthority()
+        public async Task GetAuthorizationInfoAsync_WithoutAuthenticateHeadersAndPpeAndPpeOverride_ReturnsCorrectAuthority()
         {
             var ppeUris = new[]
             {
@@ -79,36 +79,49 @@ public async Task GetAadAuthorityUri_WithoutAuthenticateHeadersAndPpeAndPpeOverr
 
             foreach (var ppeUri in ppeUris)
             {
-                var authorityUri = await authUtil.GetAadAuthorityUriAsync(ppeUri, cancellationToken);
+                var authInfo = await authUtil.GetAuthorizationInfoAsync(ppeUri, cancellationToken);
 
-                authorityUri.Should().Be(new Uri("https://login.windows-ppe.net/organizations"));
+                authInfo.EntraAuthorityUri.Should().Be(new Uri("https://login.windows-ppe.net/organizations"));
             }
         }
 
         [TestMethod]
-        public async Task GetAadAuthorityUri_WithAuthenticateHeaders_ReturnsCorrectAuthority()
+        public async Task GetAuthorizationInfoAsync_WithAuthenticateHeaders_ReturnsCorrectAuthority()
         {
             var requestUri = new Uri("https://example.pkgs.visualstudio.com/_packaging/feed/nuget/v3/index.json");
 
             MockAadAuthorityHeaders(testAuthority);
 
-            var authorityUri = await authUtil.GetAadAuthorityUriAsync(requestUri, cancellationToken);
+            var authInfo = await authUtil.GetAuthorizationInfoAsync(requestUri, cancellationToken);
 
-            authorityUri.Should().Be(testAuthority);
+            authInfo.EntraAuthorityUri.Should().Be(testAuthority);
         }
 
         [TestMethod]
-        public async Task GetAadAuthorityUri_WithAuthenticateHeadersAndEnvironmentOverride_ReturnsOverrideAuthority()
+        public async Task GetAuthorizationInfoAsync_WithAuthenticateHeadersAndEnvironmentOverride_ReturnsOverrideAuthority()
         {
             var requestUri = new Uri("https://example.pkgs.visualstudio.com/_packaging/feed/nuget/v3/index.json");
             var overrideAuthority = new Uri("https://override.aad.authority.com");
 
             MockAadAuthorityHeaders(testAuthority);
 
             Environment.SetEnvironmentVariable(EnvUtil.MsalAuthorityEnvVar, overrideAuthority.ToString());
-            var authorityUri = await authUtil.GetAadAuthorityUriAsync(requestUri, cancellationToken);
+            var authInfo = await authUtil.GetAuthorizationInfoAsync(requestUri, cancellationToken);
 
-            authorityUri.Should().Be(overrideAuthority);
+            authInfo.EntraAuthorityUri.Should().Be(overrideAuthority);
+        }
+
+        [TestMethod]
+        public async Task GetAuthorizationInfoAsync_WithTenantHeaders_ReturnsCorrectTenantId()
+        {
+            var requestUri = new Uri("https://example.pkgs.visualstudio.com/_packaging/feed/nuget/v3/index.json");
+
+            var testTenant = Guid.NewGuid();
+            MockVssResourceTenantHeader(testTenant);
+
+            var authInfo = await authUtil.GetAuthorizationInfoAsync(requestUri, cancellationToken);
+
+            authInfo.EntraTenantId.Should().Be(testTenant.ToString());
         }
 
         [TestMethod]
@@ -203,9 +216,9 @@ private void MockResponseHeaders(string key, string value)
             authUtil.HttpResponseHeaders.Add(key, value);
         }
 
-        private void MockVssResourceTenantHeader()
+        private void MockVssResourceTenantHeader(Guid? guid = null)
         {
-            MockResponseHeaders(AuthUtil.VssResourceTenant, Guid.NewGuid().ToString());
+            MockResponseHeaders(AuthUtil.VssResourceTenant,(guid ?? Guid.NewGuid()).ToString());
         }
 
         private void MockVssAuthorizationEndpointHeader()

CredentialProvider.Microsoft.Tests/CredentialProviders/Vsts/VstsCredentialProviderTests.cs

@@ -53,8 +53,8 @@ public void TestInitialize()
 
             mockAuthUtil = new Mock<IAuthUtil>();
             mockAuthUtil
-                .Setup(x => x.GetAadAuthorityUriAsync(It.IsAny<Uri>(), It.IsAny<CancellationToken>()))
-                .Returns(Task.FromResult(testAuthority));
+                .Setup(x => x.GetAuthorizationInfoAsync(It.IsAny<Uri>(), It.IsAny<CancellationToken>()))
+                .Returns(Task.FromResult(new AuthorizationInfo() { EntraAuthorityUri = testAuthority }));
 
             vstsCredentialProvider = new VstsCredentialProvider(
                 mockLogger.Object,