Support Nullable reference types

[petrsvihlik]

Motivation

To enable usage of Nullable in dependant libraries.

Proposed solution

• <Nullable>enable</Nullable>
• make appropriate places with ?

Additional context

• https://docs.microsoft.com/en-us/dotnet/csharp/nullable-references
• https://docs.microsoft.com/en-us/dotnet/csharp/tutorials/nullable-reference-types

[alanta]

Are there plans to add nullable types in the model generator as well?

[petrsvihlik]

@alanta hmm...that's a very good point and probably a pre-requisite for this. would you mind opening another issue in the generators repo (linking this one)?

regarding plans, so far it's been in the "nice to have" bucket. do you think it should have a higher priority? if so, why? (e.g. do you plan to enable Nullable in the Statiq plugin? or is Nullable something that you enable by default for all new c# projects?)