Add unit tests for player configurations and referral system

- Implement tests for player configuration creation, update, and deletion, ensuring proper handling of free and paid user scenarios.
- Add tests for referral registration, including valid and invalid referrer cases.
- Create tests for referral reward flow, verifying correct reward distribution and eligibility.
- Establish a test database setup with necessary schema for user, plan, payment, and notification models.
- Introduce helper functions for seeding test data and loading entities from the database.

internal/adapters/redis/dlq.go

@@ -0,0 +1,143 @@
+package redis
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+	"stream.api/internal/database/model"
+)
+
+const (
+	dlqKey        = "picpic:dlq"
+	dlqMetaPrefix = "picpic:dlq:meta:"
+)
+
+type DeadLetterQueue struct {
+	client *redis.Client
+}
+
+type DLQEntry struct {
+	Job         *model.Job `json:"job"`
+	FailureTime time.Time  `json:"failure_time"`
+	Reason      string     `json:"reason"`
+	RetryCount  int64      `json:"retry_count"`
+}
+
+func NewDeadLetterQueue(client *redis.Client) *DeadLetterQueue {
+	return &DeadLetterQueue{client: client}
+}
+
+// Add adds a failed job to the DLQ
+func (dlq *DeadLetterQueue) Add(ctx context.Context, job *model.Job, reason string) error {
+	entry := DLQEntry{
+		Job:         job,
+		FailureTime: time.Now(),
+		Reason:      reason,
+		RetryCount:  *job.RetryCount,
+	}
+
+	data, err := json.Marshal(entry)
+	if err != nil {
+		return fmt.Errorf("failed to marshal DLQ entry: %w", err)
+	}
+
+	// Add to sorted set with timestamp as score
+	score := float64(time.Now().Unix())
+	if err := dlq.client.ZAdd(ctx, dlqKey, redis.Z{
+		Score:  score,
+		Member: job.ID,
+	}).Err(); err != nil {
+		return fmt.Errorf("failed to add to DLQ: %w", err)
+	}
+
+	// Store metadata
+	metaKey := dlqMetaPrefix + job.ID
+	if err := dlq.client.Set(ctx, metaKey, data, 0).Err(); err != nil {
+		return fmt.Errorf("failed to store DLQ metadata: %w", err)
+	}
+
+	return nil
+}
+
+// Get retrieves a job from the DLQ
+func (dlq *DeadLetterQueue) Get(ctx context.Context, jobID string) (*DLQEntry, error) {
+	metaKey := dlqMetaPrefix + jobID
+	data, err := dlq.client.Get(ctx, metaKey).Bytes()
+	if err != nil {
+		if err == redis.Nil {
+			return nil, fmt.Errorf("job not found in DLQ")
+		}
+		return nil, fmt.Errorf("failed to get DLQ entry: %w", err)
+	}
+
+	var entry DLQEntry
+	if err := json.Unmarshal(data, &entry); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal DLQ entry: %w", err)
+	}
+
+	return &entry, nil
+}
+
+// List returns all jobs in the DLQ
+func (dlq *DeadLetterQueue) List(ctx context.Context, offset, limit int64) ([]*DLQEntry, error) {
+	// Get job IDs from sorted set (newest first)
+	jobIDs, err := dlq.client.ZRevRange(ctx, dlqKey, offset, offset+limit-1).Result()
+	if err != nil {
+		return nil, fmt.Errorf("failed to list DLQ: %w", err)
+	}
+
+	entries := make([]*DLQEntry, 0, len(jobIDs))
+	for _, jobID := range jobIDs {
+		entry, err := dlq.Get(ctx, jobID)
+		if err != nil {
+			// Skip if metadata not found
+			continue
+		}
+		entries = append(entries, entry)
+	}
+
+	return entries, nil
+}
+
+// Remove removes a job from the DLQ
+func (dlq *DeadLetterQueue) Remove(ctx context.Context, jobID string) error {
+	// Remove from sorted set
+	if err := dlq.client.ZRem(ctx, dlqKey, jobID).Err(); err != nil {
+		return fmt.Errorf("failed to remove from DLQ: %w", err)
+	}
+
+	// Remove metadata
+	metaKey := dlqMetaPrefix + jobID
+	if err := dlq.client.Del(ctx, metaKey).Err(); err != nil {
+		return fmt.Errorf("failed to remove DLQ metadata: %w", err)
+	}
+
+	return nil
+}
+
+// Count returns the total number of jobs in the DLQ
+func (dlq *DeadLetterQueue) Count(ctx context.Context) (int64, error) {
+	count, err := dlq.client.ZCard(ctx, dlqKey).Result()
+	if err != nil {
+		return 0, fmt.Errorf("failed to count DLQ: %w", err)
+	}
+	return count, nil
+}
+
+// Retry removes a job from DLQ and returns it for retry
+func (dlq *DeadLetterQueue) Retry(ctx context.Context, jobID string) (*model.Job, error) {
+	entry, err := dlq.Get(ctx, jobID)
+	if err != nil {
+		return nil, err
+	}
+
+	// Remove from DLQ
+	if err := dlq.Remove(ctx, jobID); err != nil {
+		return nil, err
+	}
+
+	return entry.Job, nil
+}