Add ability to pass in a config string for FRROs

This enables passing them and and storing them in the .frro file but no
further.

Bug: 243066074
Test: Manual
Change-Id: I5c9723e69d175a536f9739619c6b6bf3162a5027
diff --git a/cmds/idmap2/libidmap2/ResourceContainer.cpp b/cmds/idmap2/libidmap2/ResourceContainer.cpp
index a62472c..0e35904 100644
--- a/cmds/idmap2/libidmap2/ResourceContainer.cpp
+++ b/cmds/idmap2/libidmap2/ResourceContainer.cpp
@@ -226,8 +226,10 @@
           *target_resource, OverlayData::ResourceIdValue{overlay_resource->data, rewrite_id}});
     } else {
       overlay_data.pairs.emplace_back(
-          OverlayData::Value{*target_resource, TargetValue{.data_type = overlay_resource->dataType,
-                                                           .data_value = overlay_resource->data}});
+          OverlayData::Value{*target_resource, TargetValueWithConfig{
+              .config = std::string(),
+              .value = TargetValue{.data_type = overlay_resource->dataType,
+                                   .data_value = overlay_resource->data}}});
     }
   }