ci: Route NuGet restore through the CFS central package feed (#1448)

Routes CI package restore through the authenticated GraphDeveloperExperiences_Public Azure Artifacts feed (network isolation / CFS compliance). Requires a pipeline run to validate against the feed.


Copilot-Session: 9bd6fe40-0d69-4e3f-927b-8628c0ab6d34

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

Author: gavinbarron

.azure-pipelines/generation-pipeline.yml

@@ -201,6 +201,20 @@ extends:
             targetPath: '$(Build.ArtifactStagingDirectory)'
             artifactName: typewriter
         steps:
+        - task: NuGetAuthenticate@1
+          displayName: 'Authenticate to Azure Artifacts'
+
+        - pwsh: |
+            @"
+            <?xml version="1.0" encoding="utf-8"?>
+            <configuration>
+              <packageSources>
+                <clear />
+                <add key="GraphDeveloperExperiences_Public" value="https://microsoftgraph.pkgs.visualstudio.com/0985d294-5762-4bc2-a565-161ef349ca3e/_packaging/GraphDeveloperExperiences_Public/nuget/v3/index.json" />
+              </packageSources>
+            </configuration>
+            "@ | Set-Content -Path "$(Build.SourcesDirectory)/nuget.config" -Encoding UTF8
+          displayName: 'Create nuget.config (central feed)'
         - template: /.azure-pipelines/generation-templates/build-and-publish-typewriter.yml@self
     - stage: stage_build_and_publish_kiota
       dependsOn: [] # remove the implicit dependency to any previous stage
@@ -212,6 +226,20 @@ extends:
             targetPath: '$(Build.ArtifactStagingDirectory)'
             artifactName: kiota
         steps:
+        - task: NuGetAuthenticate@1
+          displayName: 'Authenticate to Azure Artifacts'
+
+        - pwsh: |
+            @"
+            <?xml version="1.0" encoding="utf-8"?>
+            <configuration>
+              <packageSources>
+                <clear />
+                <add key="GraphDeveloperExperiences_Public" value="https://microsoftgraph.pkgs.visualstudio.com/0985d294-5762-4bc2-a565-161ef349ca3e/_packaging/GraphDeveloperExperiences_Public/nuget/v3/index.json" />
+              </packageSources>
+            </configuration>
+            "@ | Set-Content -Path "$(Build.SourcesDirectory)/nuget.config" -Encoding UTF8
+          displayName: 'Create nuget.config (central feed)'
         - template: /.azure-pipelines/generation-templates/build-and-publish-kiota.yml@self
 # Downloads the latest public beta metadata. If there are changes, we checkin
 # the public metadata into microsoftgraph/msgraph-metadata, and then run the