Add to_liquid for Lutaml::Model::Serializable to allow conversion to Liquid::Drop objects

[ronaldtse]

Liquid::Drop objects can be dynamically created for Lutaml::Model::Serializable objects.

We just need to create a {KlassName}Drop class that inherits from Liquid::Drop, and create methods for every attribute.

For each attribute, return the corresponding Drop class:

• All Lutaml::Model::Serializable classes already have to_liquid
• Lutaml::Type classes:
  • Simple types: Provide a value that is Liquid acceptable.
  • Complex types: Provide a Drop class that we need to define.

This will address things like:

• Gem breaking on extraneous attributes glossarist/glossarist-ruby#104
• https://github.com/metanorma/iso-iec-2382/pull/30#issuecomment-2485891399
• Add method to_liquid to transform Expressir::Model objects into Liqui… expressir#161