feat: Improve image detection and answer file generation (#1940)

assets/win10x64-ltsc.xml

@@ -61,6 +61,12 @@
       </DiskConfiguration>
       <ImageInstall>
         <OSImage>
+          <InstallFrom>
+           <MetaData wcm:action="add">
+              <Key>/image/index</Key>
+              <Value>1</Value>
+            </MetaData>
+          </InstallFrom>
           <InstallTo>
             <DiskID>0</DiskID>
             <PartitionID>3</PartitionID>
@@ -80,9 +86,6 @@
         <AcceptEula>true</AcceptEula>
         <FullName>Docker</FullName>
         <Organization>Windows for Docker</Organization>
-        <ProductKey>
-          <Key>M7XTQ-FN8P6-TTKYV-9D4CC-J462D</Key>
-        </ProductKey>
       </UserData>
       <EnableFirewall>false</EnableFirewall>
       <Diagnostics>