Merge provider defaults into one owned copy

internal/configuration/targets.go

@@ -138,24 +138,33 @@ func overlayProviderMap(lower, upper map[string]any) (map[string]any, error) {
 	if merged == nil {
 		merged = make(map[string]any)
 	}
+	if err := overlayOwnedProviderMap(merged, upper); err != nil {
+		return nil, err
+	}
+	return merged, nil
+}
+
+func overlayOwnedProviderMap(merged, upper map[string]any) error {
 	for key, value := range upper {
 		if child, ok := value.(map[string]any); ok {
 			if existing, ok := merged[key].(map[string]any); ok {
-				combined, err := overlayProviderMap(existing, child)
-				if err != nil {
-					return nil, err
+				if existing == nil {
+					existing = make(map[string]any)
+					merged[key] = existing
+				}
+				if err := overlayOwnedProviderMap(existing, child); err != nil {
+					return err
 				}
-				merged[key] = combined
 				continue
 			}
 		}
 		copied, err := jsonvalue.Copy(value)
 		if err != nil {
-			return nil, err
+			return err
 		}
 		merged[key] = copied
 	}
-	return merged, nil
+	return nil
 }
 
 func (state *loaded) lookupProfile(ctx context.Context, id string) (domain.ExecutionProfile, error) {