Auto-loadable components

[solnic]

This adds support for auto-loading of component files using Zeitwerk. All you need to do is this:

rom = ROM.runtime(:sql, "sqlite::memory") do |cfg|
  cfg.auto_register("path-to-component-dir", auto_load: true) # <= that's it
end

Once this is enabled, whenever you ask for a rom component, it will infer fully qualified constant name based on component's key and try to load a corresponding file using Zeitwerk auto-loading, ie:

• rom.relations[:users] => Relations::Users => #{components_dir}/relations/users
• rom.mappers[:users][:listing] => Mappers::Users::Listing => #{components_dir}/mappers/users/listing

If you have top-level namespace enabled, it will be prepended automatically, ie:

• rom.relations[:users] => Persistence::Relations::Users => #{components_dir}/persistence/relations/users
• rom.mappers[:users][:listing] => Persistence::Mappers::Users::Listing => #{components_dir}/persistence/mappers/users/listing