/// This AppConfigBuilder assumes that AppConfigEndpoint and AppConfigLabelFilter are configured as Settings on Azure for the Application that needs them.
/// AppConfigEndpoint would look like this: Endpoint=https://config-dec-test.azconfig.io;Id=0-l9-s0:foo;Secret=somesecret/bar
/// </summary>
/// <param name="localSettingsFile">
/// Path relative to the base path stored in Microsoft.Extensions.Configuration.IConfigurationBuilder.Properties of builder.