Support `::name` metadata property

[timotheeguerin]

Currently we have this legacy template interpolation for @doc which will look at the internal properties of the value passed.

@doc("{name}", T)
model Foo<T extends {}> {}

playground

This parameter is broken as it requires to be an object but it looks at the internal type properties(it doesn't actually interpolate the model properties)

We added string interpolation in a goal to remove fill that gap but it doesn't actually cover the only case where the formatArgs parameter did actually work.

We should find a way to have ::name metadata property that we can use on templates args

@doc("${T::name}")
model Foo<T extends {}> {}

[sascha-wolf]

::name would also be useful for discriminated unions (#3153 (comment)).

Given the following models:

@discriminator("_type")
model Piece<T extends {}> {
  @key 
  id: ID<T>; // custom scalar to denote an ID for a given model

  name: string;
  description: string;
}

model Course extends Piece<Course> {
  _type: "Course";
}

model Single extends Piece<Single> {
  _type: "Single";
}

And a newly introduced ::name meta property, we could simplify it to:

@discriminator("_type")
model Piece<T extends {}> {
  _type: T::name;

  @key 
  id: string;

  name: string;
  description: string;
}

model Course extends Piece<Course> {}
model Single extends Piece<Single> {}