build: update nuget.config (#768)

Author: jorgerangel-msft

codegen/nuget.config

@@ -1,6 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
 <configuration>
-  <packageSources>
-    <add key="generator" value="https://pkgs.dev.azure.com/azure-sdk/public/_packaging/azure-sdk-for-net/nuget/v3/index.json" />
-  </packageSources>
+  <packageSourceMapping>
+    <packageSource key="azure-sdk-dev-feed">
+      <package pattern="Microsoft.TypeSpec.Generator.ClientModel" />
+      <package pattern="Microsoft.TypeSpec.Generator" />
+      <package pattern="Microsoft.TypeSpec.Generator.Input" />
+    </packageSource>
+  </packageSourceMapping>
 </configuration>

nuget.config

@@ -6,4 +6,13 @@
     <add key="nuget" value="https://api.nuget.org/v3/index.json" />
     <add key="azure-sdk-dev-feed" value="https://pkgs.dev.azure.com/azure-sdk/public/_packaging/azure-sdk-for-net/nuget/v3/index.json" />
   </packageSources>
+  <packageSourceMapping>
+    <packageSource key="azure-sdk-dev-feed">
+      <package pattern="System.ClientModel" />
+      <package pattern="Microsoft.ClientModel.TestFramework" />
+    </packageSource>
+    <packageSource key="nuget">
+      <package pattern="*" />
+    </packageSource>
+  </packageSourceMapping>
 </configuration>