Expose IDbConnection through DI

[mdockal]

I tried to access the DBConnection directly in a module so I can use dapper.contrib to add custom tables in my module. I added the following code in Startup.cs

 public override void Configure(IApplicationBuilder builder, IRouteBuilder routes, IServiceProvider serviceProvider)
{
     var connection = serviceProvider.GetRequiredService<IDbConnection>();
     //var connection = serviceProvider.GetService<IDbConnection>();
}

Got the following exception:
InvalidOperationException: No service for type 'System.Data.IDbConnection' has been registered.

I think this would also resolve #2248

[infofromca]

#1401