Add ability to provide config values via mounted file

Add ability to provide config values like ZFSSA_TARGET via a mounted file.

If ZFSSA_TARGET is not provided via environment variable , the code will default to the value found in /mnt/config/config.yaml file else will be empty.

pkg/utils/parser_utils.go

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2023, Oracle and/or its affiliates.
+ * Licensed under the Universal Permissive License v 1.0 as shown at https://oss.oracle.com/licenses/upl/
+ */
+
+package utils
+
+import (
+	"io/ioutil"
+	"gopkg.in/yaml.v2"
+	"errors"
+	"fmt"
+)
+
+func GetValueFromYAML(yamlFilePath string, key string) (string, error) {
+	yamlData, err := ioutil.ReadFile(yamlFilePath)
+	if err != nil {
+		return "", errors.New(fmt.Sprintf("the file <%s> could not be read from: <%s>",
+			yamlFilePath, err))
+	}
+
+	// Unmarshal YAML into a map[string]interface{}
+	yamlMap := make(map[string]interface{})
+	err = yaml.Unmarshal(yamlData, &yamlMap)
+	if err != nil {
+		return "", errors.New(fmt.Sprintf("the file <%s> could not be parsed: <%s>",
+			yamlFilePath, err))
+	}
+
+	// Get value from map using key
+	value, ok := yamlMap[key]
+	if !ok {
+		return "", errors.New(fmt.Sprintf("key: <%s> could not be retrieved from <%s> : <%s>",
+		     key, yamlFilePath, err))
+	}
+	// Convert value to string and return
+	return fmt.Sprintf("%v", value), nil
+
+}