Model Groups provide logical model names that map to multiple physical
models across providers, with automatic failover when one provider's
key pool is exhausted.
Backend:
- New model_groups + model_group_members tables with FK constraints
- Full CRUD API (7 endpoints) with admin-only write permissions
- Cache layer: DashMap-backed CachedModelGroup with load_from_db
- Relay integration: ModelResolution enum for Direct/Group routing
- Cross-provider failover: sort_candidates_by_quota + OnceLock cache
- Relay failure path: record failure usage + relay_dequeue (fixes
queue counter leak that caused connection pool exhaustion)
- add_group_member: validate model_id exists before insert
Frontend:
- saas-relay-client: accept getModel() callback for dynamic model selection
- connectionStore: prefer conversationStore.currentModel over first available
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
