feat(user): add changelog read tracking and unread count method

app/Models/UserChangelogRead.php

@@ -0,0 +1,48 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class UserChangelogRead extends Model
+{
+    protected $fillable = [
+        'user_id',
+        'changelog_identifier',
+        'read_at',
+    ];
+
+    protected $casts = [
+        'read_at' => 'datetime',
+    ];
+
+    public function user(): BelongsTo
+    {
+        return $this->belongsTo(User::class);
+    }
+
+    public static function markAsRead(int $userId, string $identifier): void
+    {
+        self::firstOrCreate([
+            'user_id' => $userId,
+            'changelog_identifier' => $identifier,
+        ], [
+            'read_at' => now(),
+        ]);
+    }
+
+    public static function isReadByUser(int $userId, string $identifier): bool
+    {
+        return self::where('user_id', $userId)
+            ->where('changelog_identifier', $identifier)
+            ->exists();
+    }
+
+    public static function getReadIdentifiersForUser(int $userId): array
+    {
+        return self::where('user_id', $userId)
+            ->pluck('changelog_identifier')
+            ->toArray();
+    }
+}