add config definition

Reviewed-on: #10
Co-authored-by: andrey <andrey@4devs.io>
Co-committed-by: andrey <andrey@4devs.io>

definition/option/tpl/unmarshal_json.tmpl

@@ -0,0 +1,8 @@
+{{block "UnmarshalJSON" . }}
+	pval, perr := {{.ValName}}.ParseString()
+	if perr != nil {
+		return {{.Value}}, fmt.Errorf("read {{.Keys}}:%w", perr)
+	}
+
+	return {{.Value}}, {{.Value}}.UnmarshalJSON([]byte(pval))
+{{end}}