Added options which allow the configuration of endpoint initialization

[mikoskinen]

Affects the endpoint initialization scenario where the api contains an ApiFactory. For example the retry policy for initialization can now be configured.

To configure settings for a single named endpoint one can use:

        services.Configure<EndpointInitializationOptions>("dynamictest", options =>
        {
            options.RetryCount = 200;
        });

Where "dynamictest" is the name of the api.

To configure the default settings for all the endpoints, one can use:

        services.ConfigureAll<EndpointInitializationOptions>(options =>
        {
            options.RetryCount = 5;
        });

To retry forever, use:

        services.Configure<EndpointInitializationOptions>("myapi", options =>
        {
            options.RetryCount = null;
        });

To send an email after 5 failed attempts, use:

        services.Configure<EndpointInitializationOptions>("dynamictest", options =>
        {
            options.RetryCount = null;

            options.OnBeforeUpdatingInitializationFailedStatus = async (endpoint, exception, retryCount, statusMessage) =>
            {
                if (retryCount == 5)
                {
                    await SendEmail(exception, endpoint);
                }
            };
        });