Add models, define relationship, revert 068fe29

* Generate model and migration using:
$ ./vendor/bin/sail artisan make:model -m Question
$ ./vendor/bin/sail artisan make:model -m Hint
* Create foreign key relationship between tables ('question_id' on the 'hints' table references the 'id' column on the 'questions' table)
*     Reverting 068fe29 and using it in combination with the (new) .env file (from PR #7 - ie. with the changed/new password) were required in order for the following to work:

$ ./vendor/bin/sail artisan migrate

app/Models/Hint.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use App\Models\Question;
+
+class Hint extends Model
+{
+    use HasFactory;
+
+    protected $fillable = ['question_id', 'hint'];
+
+    /**
+     * Get the question that owns the hint.
+     */
+    public function question()
+    {
+        return $this->belongsTo(Question::class);
+    }
+}

app/Models/Question.php

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+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use App\Models\Hint;
+
+class Question extends Model
+{
+    use HasFactory;
+
+    protected $fillable = ['title', 'body'];
+    /**
+     * Get the hints for the question.
+     */
+    public function hints()
+    {
+        return $this->hasMany(Hint::class);
+    }
+}

database/migrations/2023_04_20_223654_create_questions_table.php

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+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::create('questions', function (Blueprint $table) {
+            $table->id();
+            $table->string('title');
+            $table->text('body');
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('questions');
+    }
+};

database/migrations/2023_04_20_224629_create_hints_table.php

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+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::create('hints', function (Blueprint $table) {
+            $table->unsignedBigInteger('question_id')->nullable();
+            $table->text('hint');
+            $table->timestamps();
+
+            //set question_id as foreign key (ie. if question is deleted, its hints will also be deleted)
+            $table->foreign('question_id')->references('id')->on('questions')
+            ->onDelete('cascade');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('hints');
+    }
+};