public static string ApiUrl(this IContextVariableProvider contextVariableProvider) => contextVariableProvider.Get(nameof(ApiUrl));
 private static string Get(this IContextVariableProvider contextVariableProvider, string name)
 => contextVariableProvider.GetRequiredContextVariable(Prefix + name);
 public static string AccountID(this IContextVariableProvider contextVariableProvider) => contextVariableProvider.Get(nameof(AccountID));
 public static string SubscriptionKey(this IContextVariableProvider contextVariableProvider) => contextVariableProvider.Get(nameof(SubscriptionKey));
 public static string Location(this IContextVariableProvider contextVariableProvider) => contextVariableProvider.Get(nameof(Location));