feat: add experimental config file support

internal/utils/loaders/loader_file.go

@@ -0,0 +1,35 @@
+package loaders
+
+import (
+	"github.com/rs/zerolog/log"
+	"github.com/traefik/paerser/cli"
+	"github.com/traefik/paerser/file"
+	"github.com/traefik/paerser/flag"
+)
+
+type FileLoader struct{}
+
+func (f *FileLoader) Load(args []string, cmd *cli.Command) (bool, error) {
+	flags, err := flag.Parse(args, cmd.Configuration)
+
+	if err != nil {
+		return false, err
+	}
+
+	// I guess we are using traefik as the root name
+	configFileFlag := "traefik.experimental.configFile"
+
+	if _, ok := flags[configFileFlag]; !ok {
+		return false, nil
+	}
+
+	log.Warn().Msg("Using experimental file config loader, this feature is experimental and may change or be removed in future releases")
+
+	err = file.Decode(flags[configFileFlag], cmd.Configuration)
+
+	if err != nil {
+		return false, err
+	}
+
+	return true, nil
+}