Extend Backend Data Model for FlowNode (Attack Flow Step Metadata)

[KadeMorton]

What it is

Introduce a new backend model to store step-level metadata required for building Attack Flows in Thread.

Why it matters

• Enables us to persist user-defined sequence order and relationships (e.g., forks, merges).
• Forms the backend foundation for building and exporting flows.

Requirements

• Add new database table/class: FlowNode with the following fields:
  • id
  • technique_id
  • step_index
  • fork_parent (nullable foreign key to FlowNode)
  • merge_into (nullable foreign key to FlowNode)
  • linked_ioc_ids (many-to-many or JSON array)
  • linked_cve_ids
  • linked_malware_ids
• Write migration script for schema change.
• Update ORM layer to expose new model.
• Do not change existing Technique or IOC tables; FlowNode references them.

Acceptance Criteria

• FlowNode model and DB table implemented.
• Migration script tested and applied cleanly.
• ORM integration tested with sample insert/query/update.