Code fix: implement Create for an IValidatedValue that lacks it #82

A validated value object has one hand-written member, Create. Declaring IValidatedValue<TSelf, T, TFault> without it fails the build on the missing static member, and nothing helps the user write it: the analyzers' two code fixes cover positional Match arguments and a required parameterless constructor.

Proposal

A code fix, offered where a type declares IValidatedValue<TSelf, T, TFault> and lacks Create, that inserts:

public static Result<TSelf, TFault> Create(T value)
{
    // your rules: if (...) return Result.Error(TFault.Member);
    return Result.Success(new TSelf(value));
}

with the type arguments filled in from the declaration (the shape of the Generators README's Email). Optionally the same for a plain IValue<T> turned into a validated one.

Done when

• The fix is offered on the diagnostic the missing Create raises, for a struct and a class value object, a nested and a generic-containing one (the TypeArgumentSites and TypeArgumentKinds catalogues where they apply), and the fixed code compiles and generates.
• No new diagnostic at Error severity (a minor release); the Generators README mentions the fix where it explains Create.