Fix: Remove omitempty from required fields to prevent model corruption during risk seeding

[udvasude]

This PR addresses issues with risk seeding that resulted in the removal of required fields and corruption of otherwise valid model.yaml files. The root cause was identified as improper use of the omitempty tag during marshalling/unmarshalling.

Details:

• Removed omitempty from struct fields that are marked as required in the schema, ensuring these fields are always present in the output.
• Some fields are marked as nullable but are still required by the schema; these must not use omitempty to avoid accidental omission.