[mic][iso] Save input ISO configuration as yaml.

'SavedConfigs' is a subset of the Image Customizer input configurations that
needs to be saved on the output media so that it can be used in subsequent
runs of the Image Customizer against that same output media.

This preservation of input configuration is necessary for subsequent runs if
the configuration does not result in updating root file system.

For example, if the user specifies a kernel argument that is specific to the
ISO image, it will not be present in any of the grub config files on the
root file system - only in the final ISO image grub.cfg. When that ISO image
is further customized, the root file system grub.cfg migith get re-generated
and we need to remember to add the ISO specific arguments from the previous
runs. SavedConfigs is the place where we can store such arguments so we can
re-apply them.

Author: gmileka

toolkit/tools/imagecustomizerapi/utils.go

@@ -5,6 +5,7 @@ package imagecustomizerapi
 
 import (
 	"bytes"
+	"fmt"
 	"os"
 
 	"gopkg.in/yaml.v3"
@@ -51,3 +52,41 @@ func UnmarshalYaml[ValueType HasIsValid](yamlData []byte, value ValueType) error
 
 	return nil
 }
+
+func MarshalYamlFile[ValueType HasIsValid](yamlfilePath string, value ValueType) (err error) {
+	yamlString, err := MarshalYaml(value)
+	if err != nil {
+		return err
+	}
+
+	file, err := os.Create(yamlfilePath)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		closeErr := file.Close()
+		if closeErr != nil {
+			if err != nil {
+				err = fmt.Errorf("%w:\nfailed to close (%s): %w", err, yamlfilePath, closeErr)
+			} else {
+				err = fmt.Errorf("failed to close (%s): %w", yamlfilePath, closeErr)
+			}
+		}
+	}()
+
+	_, err = file.WriteString(yamlString)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func MarshalYaml[ValueType HasIsValid](value ValueType) (string, error) {
+	yamlData, err := yaml.Marshal(value)
+	if err != nil {
+		return "", err
+	}
+
+	return string(yamlData), nil
+}