emitEvents for Go (Gin + GORM): generate a transactional domain-event spine

[cultron]

Summary

Extend the opt-in emitEvents capability (added for TypeScript in #79 / PR #80) to the Go (Gin + GORM) generator, so that opted-in entities produce a durable domain-event spine written in the same transaction as the state change.

Today emitEvents is parsed and honored only by the TypeScript generator; the Go generator inherits the base no-op (generateDomainEvents returns []), so emitEvents is silently ignored for Go projects.

Reference

#79 / PR #80 is the reference spec. The TypeScript implementation generates a DomainEvent entity (events table), a subscriber writing events transactionally, an app-overridable mapper (event-type taxonomy + payload), a relay (drain/retry; publish() is the app-supplied delivery hook), and a global module wired into the app. Flag resolution is entity.emitEvents ?? <top-level emitEvents> ?? false (global default with per-entity opt-out). Keep the same naming and the same extension-point boundaries.

Language-specific mechanism

The durability lever is ORM-specific. For GORM:

• Use GORM hooks (AfterCreate/AfterUpdate/AfterDelete) or a registered callback/plugin to write the event row using the hook's *gorm.DB (tx), so the event is inserted within the same transaction as the state change.
• Map create/update/delete to created/updated/removed.
• Recursion guard: never emit for the DomainEvent model itself.
• Scope emission to the opted-in entities only.
• Provide mapper + relay as overridable extension points (delivery left to the app); a DomainEvent model + events table; relay drains pending rows.

Scope / notes

• Mirror the TS resolution helper and opt-out semantics.
• Document that raw SQL / bulk operations that bypass GORM hooks won't emit (analogous to the raw-QueryBuilder caveat in Feature: opt-in emitEvents per entity — generate a transactional outbox + lifecycle EntitySubscriber #79).
• Consider whether Go codegen hardening should land first (Go generation is still maturing).
• Add generator tests mirroring the TS domain-events suite.

Environment

• @apso/cli — language: go (Gin + GORM)
• Related: Feature: opt-in emitEvents per entity — generate a transactional outbox + lifecycle EntitySubscriber #79, PR feat: opt-in emitEvents — generate a transactional DomainEvent spine (#79) #80 (TypeScript implementation / reference spec)