chore(config): upgrade to gosettings v0.4.0

- drop qdm12/govalid dependency
- upgrade qdm12/ss-server to v0.6.0
- do not unset sensitive config settings (makes no sense to me)

internal/configuration/sources/files/helpers.go

@@ -9,47 +9,45 @@ import (
 	"github.com/qdm12/gluetun/internal/openvpn/extract"
 )
 
-// ReadFromFile reads the content of the file as a string.
-// It returns a nil string pointer if the file does not exist.
-func ReadFromFile(filepath string) (s *string, err error) {
+// ReadFromFile reads the content of the file as a string,
+// and returns if the file was present or not with isSet.
+func ReadFromFile(filepath string) (content string, isSet bool, err error) {
 	file, err := os.Open(filepath)
 	if err != nil {
 		if os.IsNotExist(err) {
-			return nil, nil //nolint:nilnil
+			return "", false, nil
 		}
-		return nil, err
+		return "", false, fmt.Errorf("opening file: %w", err)
 	}
 
 	b, err := io.ReadAll(file)
 	if err != nil {
 		_ = file.Close()
-		return nil, err
+		return "", false, fmt.Errorf("reading file: %w", err)
 	}
 
 	if err := file.Close(); err != nil {
-		return nil, err
+		return "", false, fmt.Errorf("closing file: %w", err)
 	}
 
-	content := string(b)
+	content = string(b)
 	content = strings.TrimSuffix(content, "\r\n")
 	content = strings.TrimSuffix(content, "\n")
-	return &content, nil
+	return content, true, nil
 }
 
-func readPEMFile(filepath string) (base64Ptr *string, err error) {
-	pemData, err := ReadFromFile(filepath)
+func ReadPEMFile(filepath string) (base64Str string, isSet bool, err error) {
+	pemData, isSet, err := ReadFromFile(filepath)
 	if err != nil {
-		return nil, fmt.Errorf("reading file: %w", err)
+		return "", false, fmt.Errorf("reading file: %w", err)
+	} else if !isSet {
+		return "", false, nil
 	}
 
-	if pemData == nil {
-		return nil, nil //nolint:nilnil
-	}
-
-	base64Data, err := extract.PEM([]byte(*pemData))
+	base64Str, err = extract.PEM([]byte(pemData))
 	if err != nil {
-		return nil, fmt.Errorf("extracting base64 encoded data from PEM content: %w", err)
+		return "", false, fmt.Errorf("extracting base64 encoded data from PEM content: %w", err)
 	}
 
-	return &base64Data, nil
+	return base64Str, true, nil
 }