/// <summary>
        /// Adds a XML configuration source to <paramref name="builder"/>.
        /// </summary>
        /// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
        /// <param name="provider">The <see cref="IFileProvider"/> to use to access the file.</param>
        /// <param name="path">Path relative to the base path stored in
        /// <see cref="IConfigurationBuilder.Properties"/> of <paramref name="builder"/>.</param>
        /// <param name="optional">Whether the file is optional.</param>
        /// <param name="reloadOnChange">Whether the configuration should be reloaded if the file changes.</param>
        /// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
        public static IConfigurationBuilder AddXmlFile(this IConfigurationBuilder builder, IFileProvider provider, string path, bool optional, bool reloadOnChange)
        {
            if (builder == null)
            {
                throw new ArgumentNullException(nameof(builder));
            }
            if (string.IsNullOrEmpty(path))
            {
                throw new ArgumentException("Error_InvalidFilePath", nameof(path));
            }

            var source = new XmlConfigurationSource
            {
                FileProvider   = provider,
                Path           = path,
                Optional       = optional,
                ReloadOnChange = reloadOnChange
            };

            source.ResolveFileProvider();
            builder.Add(source);
            return(builder);
        }