Added protected ctor to AuthenticationSchemeProvider

[khellang]

Closes https://github.com/aspnet/Home/issues/2827

This will let me derive from AuthenticationSchemeProvider, pass in StringComparer.OrdinalIgnoreCase instead of the default StringComparer.Ordinal, and swap the implementation in the container.

It does not affect registration in any way (SchemeMap in AuthenticationOptions is still case-sensitive), but it will let me do scheme lookups without having to worry about the correct casing. I.e. github and GitHub will both return the correct scheme.

Personally, I'd prefer to take it one step further by adding a SchemeNameComparer option to AuthenticationOptions (as shown in this branch). That would allow me to skip the custom class altogether and just set the property on the options object.

What do you think? Too crazy? 😄

// @HaoK @davidfowl @Eilon @Tratcher

[HaoK]

Too crazy, we don't want to be responsible for making that work everywhere if someone turned this new switch on...

[khellang]

Too crazy, we don't want to be responsible for making that work everywhere if someone turned this new switch on...

I'm assuming that was in response to my option proposal? I guess the ctor is a nice compromise 😄

[HaoK]

Yes, the idea is I'm fine making our implementations more extensible (for things like case-insensitivity), I'm not fine with trying to make case-insensitivity first class

[HaoK]

Thanks @khellang

[khellang]

Thank you! ❤