- Restructured RazorLanguageVersion to be a sealed concrete type to enable things like `RazorLanguageVersion.Latest`; it also allows us to make broader changes in the future. Also, in the future if we want to add support for overriding operators to enable greater than comparisons we can as well.
- Removed version validity checks because we restrict who can construct a `RazorLanguageVersion` now. This way we don't have to check for valid versions all throughout our code.
- Added a simple `ProjectExtensibilityConfiguration` => `RazorLanguageVersion` method in the `DefaultProjectExtensibilityConfigurationFactory` to temporarily enable letting the system operate on the `RazorLanguageVersion`. Eventually that entire class will change.
#1961
- Removed verbose `Create` methods in favor of the `RazorParserOptionsBuilder`. This is similar to how the `RazorEngine` functions.
- Added a `CreateDesignTime` method.
- Updated existing tests to use new Create syntax.
#1510
This change removes the default usings for 'System' and
'System.Threading.Tasks' and adds them to the MVC template engine.
This is preparation for removing this feature from the razor options, I
wanted to get all of the intentional diff out of the way.