RFC Nesting scalars

[SerafimArts]

Add inheritance scalars syntax:

scalar Email extends String

In this case, all behavior is completely inherited from the parent. In the absence of a parent, the behavior is reduced to type Any: https://railt.org/docs/sdl/scalar/any

[fesor]

Maybe instead of inheritance (extends keyword) provide something like aliasing?

type Email as String

[SerafimArts]

@fesor
By creating this offer, I wanted to:

1. To legalize that scheme for the redefinition of scalars, which is already present.

type A { field: Any }
extend type A { field: String } # <<< "field" type override

2. Simplify the casting system (serialization).

Having the same row as the parent, we will know that the value is converted to a string with the ability to override this behavior with the help of, for example, directives, like here: https://railt.org/docs/sdl/scalar/custom

At the moment, each scalar has a strictly wired inheritance scheme and the permissibility of overriding. Right in the code: https://github.com/railt/railt/blob/master/src/Railt/Reflection/Standard/Scalars/StringType.php#L17