Add metadata to options

[KirIgor]

In some cases it would be useful to define metadata for options while initializing.

For example we can use SmartInitializer for describing relational database tables:

class Model
  include SmartCore::Initializer

  def self.column(...)
    option(...)
  end
end

class Author < Model
  column :id, Types::Integer, metadata: { primary_key: true }
  column :name, Types::String, metadata: { unique: true }
end

class Book < Model
  column :author, Types::Integer, metadata: { foreign_key: Author }
  column :title, Types::String
end

class CoveredBook < Book
  column :cover, Types::Base64Image
end

In that case some static metadata that can be inherited would be very useful.

[KirIgor]

And some way to read:

Author.__options__.first.metadata # => { primary_key: true }