More flexibility in PreStartupChecks

[DavidBoike]

The transport performs a PreStartupCheck to ensure it can connect to the SQL Server during endpoint startup. However, when authenticating via Group Managed Service Accounts (gMSA), the endpoint can't get valid connection parameters until after the Windows Service has started.

In this case, using NServiceBus.Extensions.Hosting isn't possible because the PreStartupCheck occurs before the service is started, and cannot succeed. Users needing to use gMSA in this scenario would need to use self-hosting to host NServiceBus, losing out on the other advantages of the .UseNServiceBus(…) extension method.

One option would be to add API that allows the user to either skip the PreStartupCheck or defer it until later in the endpoint startup process.