Add country_code attribute to Security model and related classes

* Update Security model to include country_code in the data definition.
* Modify Provider::SecurityConcept to define country_code for security.
* Enhance Provider::Synth to extract country_code from security data.
* Update Security::Provided to include country_code when creating security instances.
* Adjust Security::SynthComboboxOption to add country_code as an attribute.
* Revise combobox_security partial to conditionally display country flag and code.

app/models/provider/synth.rb

@@ -106,6 +106,7 @@ class Provider::Synth < Provider
           name: security.dig("name"),
           logo_url: security.dig("logo_url"),
           exchange_operating_mic: security.dig("exchange", "operating_mic_code"),
+          country_code: security.dig("exchange", "country_code")
         )
       end
     end