Upd lutaml model to 0.8.0

Gemfile

@@ -3,6 +3,10 @@ source "https://rubygems.org"
 # Specify your gem's dependencies in relaton_cie.gemspec
 gemspec
 
+gem "lutaml-model", github: "lutaml/lutaml-model", branch: "main"
+gem "relaton-bib", github: "relaton/relaton-bib", branch: "upd-lutaml-model-to-0-8-0"
+gem "rfcxml", github: "metanorma/rfcxml", branch: "main"
+
 gem "equivalent-xml", "~> 0.6"
 gem "pry-byebug"
 gem "rake", "~> 13.0"

lib/relaton/cie/bibdata.rb

@@ -1,6 +1,7 @@
 module Relaton
   module Cie
     class Bibdata < Item
+      model ItemData
       include Bib::BibdataShared
     end
   end

lib/relaton/cie/bibitem.rb

@@ -1,6 +1,7 @@
 module Relaton
   module Cie
     class Bibitem < Item
+      model ItemData
       include Bib::BibitemShared
     end
   end

lib/relaton/cie/ext.rb

@@ -1,11 +1,7 @@
 module Relaton
   module Cie
     class Ext < Bib::Ext
-      attribute :schema_version, method: :get_shema_version
-
-      def get_shema_version
-        Relaton.schema_versions["relaton-model-cie"]
-      end
+      def get_schema_version = Relaton.schema_versions["relaton-model-cie"]
     end
   end
 end