Cookies middleware should not enforce need for ILoggerFactory

[Praburaj]

Currently when ILoggerFactory is not registered in the IoC container the Cookies middleware throws a null reference exception as this is a compulsory parameter. This has to be an optional parameter if the app does not want to do any logging.

[Tratcher]

1. If we inject ILoggerFactory via DI, you can't make it optional.
2. Hosting should provide an implementation, even if it's a NullLoggerFactory that returns a NullLogger. Individual middleware shouldn't have to deal with this.
3. Consider defining NullLoggerFactory in the Logging assembly.

[Eilon]

Yeah I'm not sure whether we want to use a null object pattern here or not. There are certainly both pros and cons (having to write null checks vs. unnecessary calls into a black hole).

As far as being optional with DI, there are two ways to achieve this:

1. Instead of injecting, use GetService (and catch exceptions if it throws)
2. Take in an IEnumerable<ILoggerFactory> and check that you got either 0 or 1 back.

I'm sure that within minutes both @lodejard and @davidfowl will read this and have simultaneous heart attacks 💔 💔 but I'm curious what they'll say.

[Praburaj]

I moved this bug to Hosting repo as it make sense to have this ILoggerFactory created in hosting. Here is the bug in hosting : aspnet/Hosting#20