Implement ProxyContactListProvider Riverpod Provider
epic-bulk-and-proxy-registration-foundation-task-004 — Create the ProxyContactListProvider as a Riverpod AsyncNotifier that fetches the authenticated coordinator's assigned peer mentor roster from Supabase. The provider must filter results by the coordinator's active chapter scope, map rows to a PeerMentorContact value object (id, displayName, avatarUrl, status), and expose the async state for consumption by selector screens. Ensure RLS policies are respected so coordinators only see their own roster.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Implementation Notes
Define PeerMentorContact in lib/domain/models/ as a freezed or plain Dart value object — avoid using database row maps directly in the UI layer. The Supabase query should join from coordinator_assignments to profiles (or equivalent) in a single call rather than two sequential queries. Use .select('id, display_name, avatar_url, status') to be explicit. If the project already has a contacts repository pattern, consider whether this provider should delegate to it or query Supabase directly — prefer consistency with existing patterns.
Add a TODO comment linking to task-005 for the caching layer that will be added next.
Testing Requirements
Write flutter_test unit tests with a mocked Supabase client: (1) returns correct PeerMentorContact list from mock response, (2) returns empty list when user is not a coordinator, (3) emits AsyncError when Supabase throws PostgrestException, (4) maps avatarUrl to null when column is absent. Write one widget test that wraps a consumer widget with ProviderScope overriding the provider, verifying AsyncData renders the contact list. Write one integration test against a local Supabase instance seeded with two coordinators in different chapters, confirming each sees only their own roster.
Adding recorded_by_user_id to the activities table and writing correct RLS policies is error-prone: overly permissive policies would allow coordinators to record activities under arbitrary user IDs they do not manage, while overly restrictive policies would silently block valid proxy inserts. A policy defect here would either create a security vulnerability or break the entire proxy feature at runtime.
Mitigation & Contingency
Mitigation: Write RLS policies in a local Supabase emulator first. Include policy unit tests using pg_tap or supabase test helpers. Have a second reviewer check the migration SQL before merging. Explicitly test the three cases: coordinator inserting for their own mentors (should succeed), coordinator inserting for another chapter's mentors (should fail), peer mentor inserting for themselves (should succeed as before).
Contingency: If a policy defect is discovered in staging, roll back the migration with a down-migration script. Delay feature release until the policy is corrected and re-verified. Apply a feature flag to keep the proxy entry point hidden from coordinators until the fix is confirmed.
The insert_bulk_activities RPC must behave atomically — a failure on row 7 of 12 must roll back rows 1–6. If Supabase's RPC transaction handling is misconfigured or if network interruptions cause partial acknowledgements, some peer mentors could receive duplicate or missing activity records, directly corrupting Bufdir statistics for the coordinator's chapter.
Mitigation & Contingency
Mitigation: Implement the RPC as a PostgreSQL function with explicit BEGIN/EXCEPTION/END block to guarantee atomicity. Add an integration test that inserts a batch where one row violates a unique constraint and asserts zero rows are committed. Document the transaction semantics in code comments.
Contingency: If atomicity cannot be guaranteed via RPC (e.g., due to Supabase plan limitations), fall back to a sequential insert loop with a compensating DELETE in case of partial failure, and surface a clear error to the coordinator listing which mentors failed and which succeeded.