feat: send email notifications for missed messages

- New cron job in cluster
- Handle presence and other concerns
- Toggle in app to disable email notifications
- Handles other edge cases such as cooldown period
- Simple html email with simple message

Closes #117

go/internal/human/service.go

@@ -3,6 +3,7 @@ package human
 import (
 	"context"
 	"errors"
+	"time"
 
 	"github.com/flowy-live/llink/internal/utils"
 	"github.com/jackc/pgx/v5/pgxpool"
@@ -16,6 +17,12 @@ type Service interface {
 	GetByEmail(ctx context.Context, email string) (*Human, error)
 	// GetByID returns ErrNotFound if no human found
 	GetByID(ctx context.Context, id string) (*Human, error)
+	// ListAll returns all humans
+	ListAll(ctx context.Context) ([]*Human, error)
+	// UpdateEmailNotificationsEnabled toggles email notification preference
+	UpdateEmailNotificationsEnabled(ctx context.Context, id string, enabled bool) error
+	// UpdateLastEmailNotificationSentAt records when the last notification email was sent
+	UpdateLastEmailNotificationSentAt(ctx context.Context, id string, t time.Time) error
 }
 
 type serviceImpl struct {
@@ -62,3 +69,23 @@ func (s *serviceImpl) GetByID(ctx context.Context, id string) (*Human, error) {
 	}
 	return h, err
 }
+
+func (s *serviceImpl) ListAll(ctx context.Context) ([]*Human, error) {
+	return s.repo.listAll(ctx)
+}
+
+func (s *serviceImpl) UpdateEmailNotificationsEnabled(ctx context.Context, id string, enabled bool) error {
+	err := s.repo.updateEmailNotificationsEnabled(ctx, id, enabled)
+	if errors.Is(err, errNotFound) {
+		return ErrNotFound
+	}
+	return err
+}
+
+func (s *serviceImpl) UpdateLastEmailNotificationSentAt(ctx context.Context, id string, t time.Time) error {
+	err := s.repo.updateLastEmailNotificationSentAt(ctx, id, t)
+	if errors.Is(err, errNotFound) {
+		return ErrNotFound
+	}
+	return err
+}