feat: Initial commit for Saqel Platform architecture, backend, Docker, and documentation

backend/app/Models/Answer.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class Answer extends Model
+{
+    protected $fillable = [
+        'quiz_attempt_id',
+        'question_id',
+        'selected_option_id',
+        'is_correct',
+        'time_spent_seconds',
+    ];
+
+    protected $casts = [
+        'is_correct' => 'boolean',
+    ];
+
+    public function attempt(): BelongsTo
+    {
+        return $this->belongsTo(QuizAttempt::class, 'quiz_attempt_id');
+    }
+
+    public function question(): BelongsTo
+    {
+        return $this->belongsTo(Question::class);
+    }
+
+    public function selectedOption(): BelongsTo
+    {
+        return $this->belongsTo(QuestionOption::class, 'selected_option_id');
+    }
+}