feat: generate GraphQL descriptions from CDS doc comments

[schwma]

Turns CDS doc comments of services, entities, and elements:

/** A Chapter of a Book */
entity Chapters : managed {
  key book   : Association to bookshop.Books;
  key number : Integer;
      title  : String;
}

into GraphQL descriptions:

"""A Chapter of a Book"""
type AdminService_Chapters {
  book: AdminService_Books
  book_ID: Int
  createdAt: Timestamp

  """Canonical user ID"""
  createdBy: String
  modifiedAt: Timestamp

  """Canonical user ID"""
  modifiedBy: String
  number: Int
  title: String
}

when compilation of doc comments in enabled in the CDS compiler options.